I can't pull up the dirgram, but in general, the O ring should be fitting into a groove. This should help keep it from moving. Then I would lubricate the o ring with something like vasoline. With the two above done, you should be able to slide the sleeve back on (working it side to side if necessary). If the o ring is still moving I would think that it's not in the right position or not in the proper groove.

iLoveRed, no worries. I think I found the answer. I definitely need an RO faucet that supports an air gap feature. This Delta faucet can be either. "If you have an under the sink RO system you need to have an air gap. If your RO is located elsewhere you do not. Good reference here." from: http://www.water-softeners-filters.com/air-gap-info  “This is the most common scenario where an air gap faucet is recommended, and here is why: For technical reasons beyond the scope of this article, it is possible to create a vacuum in the discharge line of a reverse osmosis system connected to the sink drain. If for some reason, the sink drain happened to be filled with water up to the point at which the RO discharges into the drain, contaminated water from the sink drain could be drawn into the discharge side of the RO system. The solution to this possible condition is to install an air gap in the RO discharge line. If there is an air gap in the discharge line, and a vacuum is created on the discharge line, a small amount of air (rather than contaminated water) would be pulled back into the drain line. This air would be almost immediately purged when the vacuum was relieved back to the air gap, with no ill consequences.”

When shopping for extraordinarily low prices on Amazon, be careful about the seller. Quite a lot of sellers on Amazon selling seconds and returns, and so can underprice reputable sellers. Then if you have a problem they will ghost you, and Amazon will not take responsibility either because you bought from a seller just using the Amazon platform, but not related to Amazon in any way. Sure, you should see if Amazon is offering a lower price on Prime Day. But I would not hold out to match the Delta faucet price to a $219 Moen price from an unknown seller. Also keep in mind the inflation rates since 2022.

Jocelyn Flared Metal Pendant 16" - $1300 Crystorama XAV-B8305-VG-BL Xavier 3 Light 16" Wide Pendant - $240