Instead of checking the Subject line to prevent tickets being duplicated, instead insert a ticket ID into the body and check for that ticket ID in the body to prevent tickets from duplicating due to replies not having a specific subject.

Cherwell does this, it places the ticket ID into the body, For example, within the body, you'll find the Ticket ID written out on the bottom of an email - {CMI 43EF84993H2}

Cherwell scans each email's body for the ID and places/groups that email into the correct ticket. If it doesn't contain the ID within the thread of emails, it generates a new ticket. If the ID is so old and resolved, it creates a new ticket.

Why I bring this up is because Atera tickets are duplicating whenever someone alters the subject line with either a "RE:" or a "FWD:"
Atera depends on the subject being identical to the first subject line that initiated the email OR keep the ticket # in there, which is only generated if the ticket has been responded to, when you respond within Atera, it adds "Ticket # 1234" to the subject line.

Issue with changing the subject is that it creates a new thread for the end user, which is a bad practice because end user also wants the email to be under one email, and not two separate emails.