It goes on and on if you fail once. Here is an example, I caught this arrokuda well past the supposed 30 seconds.
#Fishing timer
stuck lintel
Yeah, I think it really goes for like 1-1.5m or something dumb. Might be intended, idk
silver swan
In fact, I am pretty sure it also happens even if you don't fail.
If your in the screen where you type in the pokemon and go beyond time it'll extend the time
Pretty sure its cuz they cant kick you out or smth