Using pihole causes all devices on my network to lose internet access

Hi all, I could use some help with the following situation:

Expected Behaviour:

I've had a functioning pihole setup for the past 2 years (current raspbian, pi zero), essentially without any issues. Pihole works as my local dns server and blocks ads for all devices on my network.

Actual Behaviour:

Recently (since the update to v5), pihole works for random amounts of time (minutes to weeks) until randomly all devices on my network will complain that they have no internet access, and cannot load webpages. The only way to fix this is to change my router settings back to using my isp's default dns servers, instead of the Pi's static local ip. I just did a fresh install of raspbian and pihole today, which worked for about 10-20 minutes before devices could not connect to the internet and I had to stop using pihole as dns.

Debug Token:

I appreciate any suggestions anyone might have to get it working again. Thanks!