boss rv-3 distorting

[ode2no1]

i've got an rv-3 that works fine in reverb mode but when using delay it's distorting the repeats. for a few years i kept it at the end of my chain where it got slammed by high output from my distortion boxes and ge-7 boosting volume and midrange. i'm assuming this is the reason for the malfunction, though i could be wrong. anyway do you guys know where i should start in the process of fixing this?