I also have this error constantly : [10005.479722] MUDEC_00049: No entry for SID 174.

I'm not sure that above MUDEC_00049 is related with your mudfish credit.  Did you check Final Fantasy XIV - A Realm Reborn too?

I definitively have credit so it's unrelated to that.I checked the link for FF14 but it doesn't change anything, my ping is identical with or without mudfish

My answer was for MUDEC_0049 error so it's not related with your ping issue because it's completely different issue. However what's current ping without mudfish?  As you know, the game server is moved to another location, so its ping result is difference depending on ISPs.

My ping without mudfish is between 170 and 180, with mudfish it's between 165 and 175. The change in the server location is the reason why I tried mudfish in the first place. My ping was under 120 before that and now it just feels laggy..

:-( Unfortunately, I think 165 ~ 175 ms is best RTT even by mudfish with current mudfish nodes. Becase the game server is moved physically from US East to US West, it's expected.  If you want to get the refund, please let me handle it for you.

Do you think this will be settled anytime soon :< ?

I don't think there's a change at game server side or location so it means it's hard for your RTT to be changed. :-(

Damn, what a lack of luck :<