Use an HMR to convert a 5xx or 408 reply to a 403
Here's a handy HMR for converting reply codes. Use case would be where a downstream device does not re-route based on the 5xx | 408, but does on a 403.
You can find out more about the use of @status-line from the 6.3.0 ACLI Configuration Guide, publicy available here. Specifically, page 403.
sip-manipulation
name 5xx408to403
description Change all 5xx or 408 responses to 403
split-headers
join-headers
header-rule
name CheckFor5xx
header-name @status-line
action store
comparison-type pattern-rule
msg-type reply
methods INVITE
match-value
new-value
element-rule
name is5xx
parameter-name
type status-code
action store
match-val-type any
comparison-type pattern-rule
match-value ^5.+
new-value
header-rule
name CheckFor408
header-name @status-line
action store
comparison-type pattern-rule
msg-type