Hello,
1) But did you see that? Or who see that? What product did you add to the cart once get the error?
I don’t see the mentioned error in the staging site error logs. What cache system do you use on your production site?
2) Just set off-canvas type for the mini-cart https://prnt.sc/mx5CcOdf2Sxi
3) We do understand this but we need to find out what causes the issue. We can’t fix the problem if it appears randomly and if we even do not get the error to check that.
Regards