I've just noted that the SPID with all the TransactionLog events is also running a fair number of SQLTransaction events with ObjectName of "buildstats" or "Flush IDES", about which I...

Looks like that was it - thank you!

Strange, that's exactly what I've tried. I get "Device not available" or whatever error happens when the file's not ther. The same file copied locally restores fine. ...

Thanks, that's an interesting topic, & it may be what we're dealing with. I love "undocumented features", don't you? :^)