Mastery vibrato - slight buzz on low e string at times

[DaveNJ]

An intermittent issue - my favorite kind! Let me know if anyone has come across this before:

At times, my semihollow Guitar with a mastery vibrato will buzz when I play an open low string, which goes away as soon as I either touch the bar or the string retainer thing.

I’ve tightened the bar a bit using the center screw, but I was wondering if anyone else has come across this issue and if there is a permanent fix.

Thanks in advance