Doing a repair today I've already done a couple times and recalled this post.
Tar river has a tendency for these four bolts to work loose. Gives the appearance a bearing has failed as the entire drum flops around.
You pull the stump jumper then a metal shroud with four 17mm wrench size bolts to expose these four.
You cannot remove them completely without pulling the shaft. But if they are not damaged you can tighten them and put a tack weld. But you have to catch it quick, usually have to pull the shaft and replace. I replaced the other drum with grade 8 bolts , lock tight and a lock washer so far so good.