I thought though may be wrong that the mondy drums were held on by the bearings ?.
If the drum is trying to move ? ,it may have developed a ridge on the outside inner edge of the drum stopping it from moving off, hard way I'm afraid with force, you have taken out any screw holding drum on ?
Sorry can't remember if they are integral bearing housing or not.
tabetha
ps remember to grind off any ridge when you do get them off.