php - mod_rewrite is behaving strangely - some RewriteRules work and others don't

I have a list of about 40 RewriteRules, all pointing to the same page, but with a different query string.

Most (37) of the rewrites work properly. Here are examples:

RewriteRule ^absa/?$ /register.php?company=absa [NC,L]
RewriteRule ^crc/?$  /register.php?company=crc [NC,L]
Copy code

But 3 of them don't work at all and throw a server error. They aren't any different, as far as I can tell.

RewriteRule ^bv/?$  /register.php?company=bv [NC,L]
Copy code

I've tried restarting Apache, I've visitedregister.php?company=bv and it works just fine, and I'm all out of ideas.

Anyone know what might be going on?

Thanks.