After updating to v5.2.1.9 (why is there no '5.2.1.9 in the 'Affects Versions' dropdown, btw?) I got the following error on one of my VivioTech VPS Lucee instances:

When I went to the web admin and tried to verify the cache connection it simply returned 'ERROR'. I ended up deleting and recreating the cache and the site came back up.

I will add further notes if this behavior returns (e.g. after some period of inactivity on the site, which is what I suspect the underlying issue to be).

I originally downgraded the server and set the update to manual, but somehow the server keeps getting updated to 5.2.1.9 despite having set that (perhaps VivioTech has a script that updates them, perhaps your 'manual' selection is borked - not sure which yet, will report another bug if I determine it's Lucee and not VivioTech), so now I'm trying to figure out how and why I'm getting this error instead of just rolling it back. Have the latest ehcache extension installed (2.10.0.21).

Using code from: https://github.com/ddspringle/framework-one-secure-auth
Demo server at: https://sa.vsgcom.net/ (the instance having this issue)