What are some signs that a therapist may have poor boundaries with their clients?

Routinely going over the time limit with certain patients, compromising the time for the next client.

Serious disappointment when the client cancels a session.

Off the top of my ancient head:

My stepdaughter’s mom tells her I’m not a real dance teacher, but my stepdaughter has seen me in action. Why does she still question my abilities?

Disclosing feelings, fantasies, and experiences to the client in ways not related to the work the client is engaged in.

Eager anticipation (or anxious anticipation) of the next session in ways that distract.

Sense of competition with persons who are important in the client’s life.

Joey Chestnut, barred last July, returns to Nathan’s hot dog eating contest - The Washington Post

Obsessing about clients outside of work hours.

Failing to mention the client in supervision/consultation, out of fear the supervisor/consultant will advise return to ordinary healthy boundaries.

Struggling with fantasies of deeper connections with clients, whether sexual or parental or other intense or intimate relationships beyond psychotherapy.

Why is Matt Gaetz being investigated but not Sarah (Tim) McBride? Why do we only care about grooming when it's the Republicans doing it?

These items can happen fleetingly, briefly, in any therapy, but if they’re frequent, it’s definitely time for the therapist to get some good, solid supervision/consultation.

Session-expressed curiosities about client details not relevant to the therapy.

General Introduction to Boundaries from Panahi Counseling:

California doctor to plead guilty to supplying Matthew Perry with ketamine - BBC

Frequent phoning or texting of clients to “check up on them and make sure they’re OK.”