They don’t still make the High Standards, unfortunately.
.22lr by nature is a very dirty burning cartridge. Low pressure, small charge, low velocity, coated/exposed lead bullets, etc. all contribute to this. Definitely start to work on a good cleaning regimen if you have not already. That Trailside is a pretty serious precision/competition pistol and will have really tight tolerances and a match chamber, compared to most other rimfire pistols, even some particularly “accurate” ones. Buckmarks, 22/45s, Victory’s, Mark I-IVs, etc. are not in the same league as this or the other high end match pistols and have more focus on reliability than supreme accuracy.
I do not own any target pistols of this caliber, as speed is more important than absolute precision for what I do, but I do know a bit about them from some of the guys I shoot with. Because you mentioned shooting Tac22 and later Aguila, are you feeding both coated lead bullets and jacketed/plated bullets through this pistol? If so, that is something that should be diligently avoided. It will expedite fouling and cause all sorts of issues, and will ruin a very nice pistol if done too much (any barrel really).
If so - Copper wool (ChoreBoy, brand name) around a nylon brush and scrub dry (no solvent). Then go through the normal solvent routine for cleaning. Follow with Iosso or JB bore paste. A few more of the solvent/dry patches. Quick scrub of Iosso/JB. Patch out one more time. You should never need to do this again, if you switch to coated lead only (again, highly advised for a Hammerli pistol).
If not - likely a piece of crud got somewhere it shouldn’t have. A good breakdown clean every 1,000rds or so, and quick cleans every 1-200rds is a good rule of thumb. Be sparing with lube, it attracts crud as a side-effect, undermining its own usefulness. Wilson Combat has a very good video on how/where to lube pistols, if needed. They use a 1911, of course, but it applies across the board.
Another note:
Number/color/something to identify your magazines. When you have a failure. Note which magazine and how many rounds (full, middle, last 1-2rds, will be good enough for failures during a match). This way you can go back to a log book or match booklets and look for trends with particular magazines.