Sorry, I should have mentioned that this is an AOLserver 4.5 system running on Linux.
I have also just tested it on one of our Windows Naviserver installations, and while it seems to be much less frequent, there still are a number of the same errors (both types) in the error log.
On a clean OpenACS 590 Windows Naviserver install, there is only one error, which is expected, the first time the tcl_url2file is accessed:
[25/Sep/2017:16:39:45][6356.718][-conn:openacs:2-] Notice: RP (37 ms): error in rp_handler: can't read "tcl_url2file(/admin/site-map/)": no such variable
