My 2865ax now loses the internet 2 or 3 times a day. This started about a week ago and I have not changed any settings.

I am with Plusnet. A reboot always brings it back until next time.

Is there anything in particular I should check?

If it started only recently, ask Plusnet to investigate if there's a fault.

Posting stats from your 2865 here might throw a bit of light on what is going on.