M1 mini issue with dual monitors

Recently was able to get an M1 Mini,16GB, 512SSD and upgrade to Sequoia then Tahoe. M1 is rated for dual monitors of up to 4K and 6K. My two are 2K Lenovo D221's that I have used for years on an i7 MacBook Pro with a Display Link adapter for one and the other through the Thunderbolt port. No problems with them ever. On the M1 though, the D221 through the USB-C port will intermittently refresh for a second and come back up without having even stoped anything that you were doing on that screen. The HDMI D221 has no issues. These are 2K monitors so well under the specs Apple says should be OK. Any ideas as to the cause of the problem? Between this and the way they have buggered up Mail, Energy and other functions I am going nuts on this thing. The D221 has refreshed twice while typing this. Thanks for any help that you can give.