Corrupted external HD, some files get recovered others don't

[Jonathan808]

I've had a issue from a External HD a while back, luckily everything seems to still be on the HD.  For some reason Recuva will only recover some information, others wont budge or will budge a bit and it will seem like after 30%, or let's say 72% for another example it wont budge to recover the rest. It's also in random areas for another example, I'm recovering music. Some will recover smoothly others wont recover at all, or it will recover for a moment than stall and the estimated time will start rising 1,2,4min ect., the same goes for trying to recover pictures in a whole different folder. Just trying to figure out why and a way to fix this problem so I can recover everything or as much as possible.