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

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

Off the top of my ancient head:

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

Here's Where Traders Expect Broadcom Stock to Go After Earnings - Investopedia

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

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.

Japanese queue for hours as rice shortage deepens - Financial Times

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

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

General Introduction to Boundaries from Panahi Counseling:

CD Projekt Red clarifies Unreal showcase of Witcher 4 was tech demo, not gameplay - GamesIndustry.biz

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

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.

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

Scientists are experimenting with a completely new approach to combat human aging - Earth.com

Serious disappointment when the client cancels a session.