Format of the part is l=<id>-<date>-<number> (as it is written in comment), but algorithm fail to parse date correctly when <id> contains '-' character. In our case the part looks like: "SERVER-SBS-120426125432Z-255".
Any chance you could create/share a small test file that shows up the problem? We can then use it to test the fix, and to ensure it doesn't get broken again in the future
No test-file available since a long time, therefore hard to reproduce and fix this currently. Please reopen with a sample file if this is still an issue for you.
This can be marked as a duplicate of bug 57744. Apologies for not noticing the connection when I opened #57744...