These are programmer errors resulting from misuse of the debugging tools' programmers' interface. You could have avoided an occurrence of one of these by using some routine to check the use of the routine generating the error.
[ Condition]
debug-error
This condition inherits from error, and all user programming errors inherit
from this condition.
[ Condition]
unhandled-condition
This error results from a signalled debug-condition occurring
without anyone handling it.
[ Condition]
unknown-code-location
This error indicates the invalid use of an unknown-code-location.
[ Condition]
unknown-debug-variable
This error indicates an attempt to use a debug-variable in conjunction with an inappropriate debug-function; for example, checking the variable's validity using a code-location in the wrong debug-function will signal this error.
[ Condition]
frame-function-mismatch
This error indicates you called a function returned by preprocess-for-eval on a frame other than the one for which the function had been prepared.