Q: my entire macmini is glitching since software update

Sometimes incompatible software from an older system, slows or

does not run at all in a newer one. This is among the source of an

issue such as you generally describe.

And sometimes items people mistakenly believe will help their Mac

will do damages to the file system, break the macOS, and ruin apps.

A fairly general topic. Do you have any specific instances or proof of

concept, or examples of the issue you are finding problem with?

Details are important. However something as simple as a list of the

configuration specifications and basic software/hardware of your Mac

can be helpful. You could read http://etrecheck.com/#about and see

if the report it can generate may be helpful; if you post it here, some

one can read through to see how that may contribute to your issue.

Sometimes a new browser update or upgrade can cause a specific

problem; I've a few different Macs with varying ages of macOS X.

So I see a variety of issues; some of them were solved in newer OS.

But do not expect a problem to be solved through upgrade, usually

what happens is some older problem or incompatible software is

carried forward to plague the poor macOS in a newer rendition.

That is because an upgrade over existing system has your older

user account and anything you installed can be in the Mac still.

Hopefully you can have a stern conversation with that Mini and tell

him to straighten-up and fly right. In the meantime, system logs

and other items may be able to point to a cause. Trouble with log

files, many people do not understand most of the content. Me too.

In any event...

Good luck & happy trails!

Just what bugs and glitches are you experiencing?