i got the same problem, had this morning 5499 subs and now 5300 so lost lots of subs, i even can't sub to other channels, it is getting crazy, i reported it as a bug many times but so far nothing did happen
my friend loses like 50 subs a day, this is no fun no more, if there was an other site the same like youtube, i would change site, sadly youtube won't fix our problems