Thanks for the reply Brian.  I'm unable to get on the server until January 10th to have a look at some of that, but I will definitely have a look once on there.  My time spent looking into LDPS so far was on another server that isn't having the issue, but that's also making me realize that I can't find any meaningful configuration options or other log files for LDPS that could help.  That's why I was hoping for some ideas on how LDPS is typically troubleshot or configured if at all.

Schedule conflicts along with government production server protocols are making this tricky to troubleshoot in an timely or interactive way, so all the ammo I can get going into the remote session will help speed this up tremendously.

LDPS is meant to not require any configuration, and it's pretty rare that the default settings need to be changed. That said, the config file is C:\Program Files\Laserfiche\Document Preview\Config\LdpsConfig.xml. There's no UI for it, so all changes are manual. You can do a few things, like set the path it uses for its temp files, if that turns out to be the problem. If you don't see enough info in the event viewer to determine what the problem might be, you can change the log level to Informational to gather more information.

Any change will require recycling the app pool before they take effect.

That matches what my experience has been so far, especially while not finding much in terms of configuration.  I will check the LdpsConfig.xml file when on the server and see what else I can find in the event viewer or other locations.  It's not clear what might suddenly be the cause for the behaviour we're seeing, but all I can think of is that perhaps it's starved for memory or space somehow and so LDPS cycles documents out of the cache fairly aggressively.

Looking at the other server, I see the EventLogLevel setting is set to Critical, which must be the default.  What other options are available?  "Debug"?

I also see some other settings that might be relevant t, such as MaxLogAgeDays, CacheDirectoryLimit and MaxCacheDays, but they're all blank.  Does LDPS assume a default in that case?

Logging options are: Critical, Important, Informational, Debug.

Right, no value set in the config means that it uses defaults specified in the code. E.g. for cache age, it's 5 days. It's possible there's something around the cache being cleaned up that's causing a problem, but that's a case that it's meant to be able to handle.

Thanks, I'll get on the server on Wednesday this week and have a look at what's up.  Hopefully there's something in the event log that gives me an idea of what's going on, but either way I'll post back with what I find.

I have some more information on this issue that will hopefully shed some light as to what's going on.

First off, disk space or memory don't seem to be issues here.  Also, all the LdpsConfig.xml file settings are at defaults.  Logging was set to Critical only, and there were no log files at C:\ProgramData\Laserfiche\LDPS\EventLog.

The C:\ProgramData\Laserfiche\LDPS\Cache folder is about 150 MB and contains 1584 files including SVG and the LDPS.sqlite database file.

I'm definitely able to see new SVG files getting created if I preview either a new Office document or do the check out and back in method I described in my original post above.

Where things get interesting is with the attached error.  There are many of these errors in the Event Viewer, and I was able to generate more by trying to preview documents that I know had been previously previewed only a few days ago.  For some reason they're typed as Information and not and Error or Warning, but the messages seem to correspond to LDPS trying to access a previously cached SVG file but it's no longer in the Cache folder.

What's not so clear is why SVG files are going missing from this folder.  Could we be bumping into one of the settings like CacheDirectoryLimit?  If it's part of normal LDPS cache operation and cleanup, then wouldn't the database be updated accordingly so it didn't think a file was still in the cache? 

There are two really old SVG files from 11/24/2020 and 11/25/2020 in that folder, but the rest are from 2/16/2021 and on, which is a pretty big gap.  Does cache cleanup focus on oldest files first?

As far as I can tell, nothing else is deleting files from that folder, but I'll see if we can monitor for that.

Can you provide all the in-code defaults for the LdpsConfig.xml file settings?  I can't seem to find them documented anywhere.

I'm a bit stumped here for the moment, but hopefully someone can help shed some light on my findings and we can figure this out.