Your problem (like several other mysterious problems with ET) is occuring because the client has multiple choices and isn’t making the correct one.
Locally, I had 3 different pk3s with Caen.bsp:
caen_beta.pk3
ti_caen_beta.pk3
caen.pk3
Whenever I played the demo, ET chose the wrong map (caen_beta.pk3, I suspect), which caused problems since a bmodel was referenced in the demo that didn’t exist in the bsp that got loaded.
I was able to play the demo fine by moving the other pk3s to someplace where ET couldn’t read them. The pk3 I used (which matches the one that was on the server in the demo) was:
-rw-r–r-- 2 rain users 6424228 2003-11-26 09:07 caen.pk3
MD5: 90fa07b2b7ce879195522a663bb1befe
SHA1: 7bf4aff646ffeee3c98974a096bd5e6f296ddfc0
ET: 5fd8b360