Repair JL Audio F112 or buy new Rhythmic, SVS, or ??

It's a shame that JL Audio quality is not better. Tough call on repairing but if you're stereo subbing your mains, the repair may make the most sense as two F-112s are nothing to sniff at performance-wise.
I just acquired an SB-3000 (sealed) for my main audio only system and it is competing very favorably against an old $3200 R.E.L. Britannia B1 (which is ported).  It's blended with rather quick Raidho D2s and is pulling off the job very well. The SB-3000 is easily in-room flat to 31hz, the B1 will hit 25 with its port but I have no music that low. (Both are audibly invisible, thankfully crossed low.) And, I tried an SB-2000 (one of two for home theater, also just received) with the D2s and was really surprised.

Hsu Research, imo, has been manufacturing high value subwoofers for a long, long time. They seem to be one of the originators of that lower end market. Now we have other good brands like SVS, Rhythmic, and others.
Good luck figuring it out. A local repair might be most cost effective and preserve a nice system.

Guys, that first youtube link shows port chuffing on a Hsu subwoofer with those triangle ports.  Granted, this is an extreme example with very low bass that you would not normally get (probably in the 20-35 hz range).  Nothing against Hsu in general, but it does show what happens when air movement becomes too much for a certain port design.

I forget to mention that there's an excellent source of information here:

https://data-bass.com/

I should mention, that in my rooms I can get down to 16Hz with the ports sealed with a single Hsu.

It seems I have found the best answer. I wrote to JL Audio, calmly explaining the issue. Given the history of repairs to my subs, they offered to fix this one under (the long expired) warranty. A generous offer and one I expect to accept.