Potentially and quite possibly but without more info impossible to be sure.

What did the contractor say in response to your concern?

yes

Thanks. I have another post somewhere on here about my floor joists. I wanted a walk-in shower in primary bathroom. The contractor notched every floor joist to make room for the shower pan. A few had addition holes for plumbing and one joist was cut completely off (span of about 4ft) under our secondary bathroom.

When I spoke up about the drywall cracking in other rooms he told me my house was old and these were pre-existing issues. (We had just purchased this home)

When I sent him the structural engineer report he told me I had structural issues outside of the bathrooms (noting that I had a crack from the corner of my bathroom door).

This guy is a bad contractor, I know that now. How do I prove the structural issues I’m seeing right outside the bathrooms (dining/kitchen) are from his hack job?

Unfortunately, you have to open everything up and see what your engineer is talking about and fix everything the right way. Did he inspect while everything was enclosed?

In the future don't let plumbers play carpenters in your house, especially plumbers who don't know what they doing, they are known to cut everything up and blame their grandmother when there is a problem.

Yes, we have a crawlspace so he was able to see it from below. I had a drop beam placed to remedy the floor joist issue. I’ve already re-done all the bathroom tile because he didn’t put any moisture barrier in. (Just tile on sheetrock/backer board)