It seem like the 3X4 don't last I read a few reviews that have the same problems, the 6x8 that cost like 50 bucks they never go out, these cheap 8 bucks switch well you get what you pay for.I use a Zinwell SAM-3402. But repeated failures suggest you have a grounding issue like a loose F fitting or more serious problems. I'd look it all over.
You are not following me, I have like 6 multi switch connect, 5 are 6X8 they have been working with No problem over a year or so. Then I have one 3X4 that will work maybe 3 or 4 months, then No signal they are just BUILT CHEAP and won't last, because any switch you are going back and forward they will go out that is made cheap, like a Disegc SwitchIF you add or remove powered coaxes to any switch, you take the real chance you are going to fry it. Don't do that.