Glad you found the issue, and I did the same thing to reinforce my trackbar's mounting bolt hole, I welded a hardened washer around the hole.
Keeping that bolt tight enough prevents that hole from wallowing out as well as helping to keep Death Wobble at bay. 45 ft-lbs. on the newer TJs is the factory tightness if I recall correctly but I like it even tighter than that so I went with a hardened bolt that can withstand being tightened more. Mine is probably at 65-70 ft-lbs. For newer metric bolts, that would be a 10.9 rating, or older SAE bolts, either a Grade 5 or Grade 8.