Lookup in flow does not work when incident gets updated through external emailaddress

[AdamUMC]

Hi there,

I have flow with a lookup. The lookup is being executed as soon there is an incident that meets the following conditions:
1- State changes from "Resolved"

2- State changes to "In Progress"

The lookup is the first action within the incident table and looks for the incident with the SYS_ID from the trigger incident records. This lookup action works very well, but only in the following cases:
1- When the incident reopener is the Caller (who has it's own ServiceNow account)
2- When the incident reoper is a backend incident agent
3- When the incident reopener id someone else with an ServiceNow account sends an mail to the incident

In this cases the lookup does not work and the flow is showing an error:
1- When the incident reopener is someone else, using a general (non-personal e-mailaddress/mailbox), internal mailbox
2- When the incident reopener is someone else, using a general (non-personal e-mailaddress/mailbox), external mailbox
3- When the incident reopener is someone else, using a personal external mailbox

I tried several solutions:
1- Changed the order of the flow actions and the datapills I was using
2- Created a subflow that runs as "System User" (the main flow runs as "User who initiates session") and runs as soon the error occurs in my flow ("Error handler")
3- Changed my lookup action from "Look Up Record" to "Look Up Records" (with plural).

None of these solutions work. The plural action does not show any error, but the problem keeps happening.

Any idea how I can solve this? Thanks!