I have had your same problem/frustration in regards to multiple disc box sets. An example is a 5 disc box set 4 discs will be in order and the 5th will be 4 discs away.I took the bait last year and went from vers. 23 to 26 upgrade I think it was. I noticed no improvement of performance and no new features (that I needed) and no sign of missing albums in library that I have been dealing with for several years. See I have albums in folders on my drives that simply do not appear in Library after an import. And the tags are all fine. It’s odd. The new version did the same thing and failed to find them.
Another thing that happens is that a six disc box set often shows the volumes out of order on pane list. I am aware that these discs were not set as 1/6, 2/6, 3/6 and so on. They are all #’d as disc one of one or 1/1. I feel that they should be in order of the album tag volume. Like Bitches Brew Session - 1, and Bitches Brew Sessions - 2, etc. if discs are not numbered then album tags with - # should be the default. But nope, I asked about it in the forums and was told that it does not always default to album title with number added. Ok. But sometimes it actually does do that. Just not a for sure thing.
So I think I’ll sit out JRiver for a good long few years before I consider an upgrade again. I think they are overdoing it a bit more than they should.
Fortunately I got completely frustrated with my Intel NUC due to fan noise (they have a mini hair dryer fan in them) I switched to my new Fanless Windows 10 PC and besides there being ZERO PC noise my JRiver works at least 10 times better due to the new PC. Now when I add multiple box set discs they are in order, my tagging and artwork changes if I need to do that stays iron clad. I am even more happy with my JRiver now and has more to do with getting rid of the horrible NUC I had.
Side note: some of you know I am pulling out my cabinet based rig to a new room that will be rack based. Out of all the gear I have pulled, wiped down, hand cleaned all interconnects, and air blew the equipment, nothing had pulled in the dust and was overloaded with dust at the fan intakes then the Synology NAS I have, I was really surprised.
I found and have use a very good air blower, I was using can air blowers before and they are never that good but this one from Amazon is fantastic. AMAZON AIR BLOWER