'which' behaves inconsistently on different machines - Why the difference?

My company has multiple servers that were setup to be identical. After using dev32 for several weeks, which stopped functioning. I go to dev35 and get similar behavior -- works for several weeks then one day it stops. dev36 is ok for now, but following this pattern I'll eventually run out of systems to use. Any thoughts on what could be causing this behavior?

dev32 ~> which python3
python3: Command not found.
dev35 ~> which python3
python3: Command not found.
dev36 ~> which python3
/bin/python3

dev32 ~> ls -al /bin/python*
lrwxrwxrwx. 1 root root     9 Jan 17 10:18 /bin/python3 -> python3.6
-rwxr-x---. 2 root root 11328 Nov 16  2020 /bin/python3.6
-rwxr-x---. 2 root root 11328 Nov 16  2020 /bin/python3.6m
dev32 ~> echo $PATH
.:/bin:/sbin:/usr/bin:/usr/bin/X11:/usr/bsd:/usr/sbin:/home//bin:/usr/local/bin:/usr/local/etc:/usr/local/sbin:/etc:/usr/etc:/usr/gnu/bin

dev35 ~> ls -al /bin/python3*
lrwxrwxrwx. 1 root root     9 Jan 17 10:11 /bin/python3 -> python3.6
-rwxr-x---. 2 root root 11328 Nov 16  2020 /bin/python3.6
-rwxr-x---. 2 root root 11328 Nov 16  2020 /bin/python3.6m
dev35 ~> echo $PATH
.:/bin:/sbin:/usr/bin:/usr/bin/X11:/usr/bsd:/usr/sbin:/home//bin:/usr/local/bin:/usr/local/etc:/usr/local/sbin:/etc:/usr/etc:/usr/gnu/bin

dev36 ~> ls -al /bin/python*
lrwxrwxrwx. 1 root root     9 Jan 17 10:18 /bin/python3 -> python3.6
-rwxr-x---. 3 root root 11328 Nov 16  2020 /bin/python3.6
-rwxr-x---. 2 root root 11328 Nov 16  2020 /bin/python3.6m
dev36 ~> echo $PATH
.:/bin:/sbin:/usr/bin:/usr/bin/X11:/usr/bsd:/usr/sbin:/home//bin:/usr/local/bin:/usr/local/etc:/usr/local/sbin:/etc:/usr/etc:/usr/gnu/bin

Even after cd /bin, which cannot find python3 Other knowns: - All servers are CentOS 7.9, uname -a matches - Ran rpm -qa | sort > $HOSTNAME.txt on each server and compared. results are identical - bash v4.2.26, tcsh v6.18.01 (same across all systems) - Behavior confirmed by multiple users; tcsh & bash yield same results. One user's shell uses system defaults (no ~/.bashrc, ~/.tcshrc or ~/.login), I customize mine. - IT says they haven't changed anything beyond standard monthly patching that is applied consistently to all servers. - Problem persists across reboots Please let me know if more information is needed.