A lot will depend on which way the joists run in the room and exactly what the source of the squeaks and humps are due to. You might be able to get by with using a flush cut saw, but if the cabinets are resting on the subfloor on a joist that will need to be sistered or otherwise beefed up and not sitting the right way, they will have to come out. Yes, you will need to replace the entire subfloor, and that will need to be done from above. I think it's time you cut a hole in the floor and did some exploring as to your joist's unsupported length, depth, and height. Cut a hole where the hump is, and see what you see. A lot of times, that's where a cross beam supports long span joists in the center and they aren't really robust enough so that lets them sag on both sides. That's where sistering the joists may come in. You can't tell until the floor and subfloor is gone.

I'm not a pro, but I've been doing a lot of research about this exact issue in the last month, in preparation for a DIY project. (I was a professional woodworker before retiring, just not a flooring person). I just want to reiterate one thing about Luaun and to suggest what I think is the reason for the failure. First, luaun is plywood, and, yes, it is commonly used, but it's a poor choice. It's smooth, but has many voids, which can compress after the vinyl is installed, with results similar to what you already have. Do not let them use luaun. The birch plywood mentioned above is good. Multiply is one brand name that is carried by my local Home Depot. It's 5mm thick. As for what happened, I don't think what you are seeing is the underlayment having moved or buckled. Rather, I think they simply layed the vinyl over an uneven underlayment. Sometimes it can take a while for the vinyl to "sink" into the gaps, so you start out with a floor that looks fine. But as the months go by, things begin to get uglier. The only reason I point this out is to suggest that you be skeptical of any claims they might make about your house settling or "unknowns" or whatever. Now, if you had walls built below this floor or something in the meantime...and they pounded them in, it's possible this could lift a few joists, causing something like this, but, setting that aside, your 30 year old house probably did most of it's major settling a few years back. Essentially, I mean to say that they did it wrong, period. There aren't any "unknowns" here that they can summon up to garner your sympathy. As for the appropriateness of installing Multi-ply (not luaun) directly over your existing vinyl, I'm not qualified to judge. My suggestion would be to call another flooring expert in to have a look. Tell him/her in advance the reason for the visit and offer to pay for an hour of time. The frustrating part about this stuff is that, even if the folks who installed this are willing to work with you, they may not be qualified to fix their own work. I wish you well.

You can pick out that filler depending on what they used - I tried it just to make sure in case we wanted to use something else/tile in the future as I used a lot of screws. I didn't want the kitchen higher than the living room. It would be a nightmare to do, but you can do it. The luan is what is causing the problem - that needs to be pulled up and replaced with plywood not luan. Standard practice is luan and no one we talked to was willing to use nicer plywood even at our insistance. Luan is the smooth surface - the didn't need to use something different. We made the choice to use better plywood as we choose DIY/better materials with the money we saved on labor (so, we probably aren't saving any money and its a lot of work, but we are getting some better stuff). Even if you put the vinyl under the cabinets, vinyl is easy to cut, but it also depends if they used the glue down method vs. tape. We taped ours down just in case I wanted to change my mind in the future or we ruined it redoing the hardwood floors or something else given we are redoing the rest of the house. We glued our one seam under the fridge and we probably didn't need vinyl under there but we have the ice maker and I know what's under there (I also put it under the oven but not dishwasher except where I could reach). The real questions are how did the put it down and they probably are trying to do what is easiest for them. I would want the 1/4 inch luan removed and replaced with 1/4 plywood, screw down (not nail) with deck screws so they will not rust and are solid and they need to be counter-sinked, it filled (let it set for a few days), sanded smooth, then use the tape method for the vinyl, cover with molding. (I did everything but lifting the plywood and the molding myself (husband did that), so it is an easy thing to do, so don't let them tell you how hard it is and I am not a big woman). Putting down vinyl is one of the easiest things we've done (and windows surprisingly). Debi, were you the one who they put the wrong color in? If you were, I'm not so sure given this is the second mistake, I'd want them fixing it.

does the HF tool take blades from other brands? I'll buy a few extra blades when I buy it but it's over a 30 min drive and I'd rather not drive that far just to get a replacement blade. I'm gonna try to get over there on Friday. not sure if i'll make it tho. i was out today doing a few errands (HD, Dollar Tree, W, gas in car) and doing that much exhausts me. I'm usually wiped out the following day - but tomorrow I'm hoping to start drilling holes to put up braces for some closet shelves (so I have a place to put boxes I take over there). not sure I'll be in any condition to drive that far on Friday. maybe Saturday. today I got some bullseye primer to use on the particle board shelves. I'm hoping the smell of that stuff doesn't kill me - lol! Also got tiny prybar to use in taking out the baseboards. looked at new baseboard. what's in now is 2.5 in high and very,very flat. they also didn't seem to care the cuts on one wall weren't filled in. looks tacky. I guess in a few rooms that's not a big deal because there'll be furniture in front of most of it. Like a few larger cabinets in the craft/store room. in that room I'll try to reuse what's up now but in the LR/DR (open area) I'll probably put up new.