R33 cluster, tach issue

[G2crash]

I have an R33 cluster in my s14. I did the wiring according to the guide and the tach worked fine till recently. basically the tach has just gradually starting crappin out. while driving, it goes from working fine, to twitching all over the place. or it just sits a bit below 1k rpms and doesn't go anywhere.

it worked fine before so I know the wiring isn't wrong. I went over it all again and double checked my connections, i've also tried a different ecu. I really don't want to tear it all apart and rewire the 14 cluster back again.

all my searches I've done are bad wiring and after market tachs and so forth. sorry if I missed something but what are my options?