Well Liz if you are acustomed to working on your plumbing as in replacing ballcock ,remove and install toilet and snaking drains I'll walk you through some things. Otherwise I don't have ideas to help you solve it. So what's it gonna be ,are you ready to get your hands dirty or do you just need a silver bullet ?

I suspect something similar - that there's a problem with the drain.

This is a new house and it's a warranty issue with the builder. Make sure they address it soon.

The definitive way to find out what is going on is to have a video camera sent down the toilet drain line. This is a very common procedure and just about any drain cleaning company can do it. If there's a problem with the drain line, this will find it. Your builder should do this.

Typically a builder will put-off, take half measures, etc. to fix significant issues until the warranty has expired. Don't let that happen. Be assertive and have them scope the drain with a camera.

The fact that it has clogged repeatedly with toilet paper is enough to suggest a larger issue and all of the symptoms together support the probability that there's a problem.

@klem1: Did you get up on the wrong side of the bed this morning?

The tub making the toilet bubble is a clear indication that the drain venting was improperly installed. The bubbling occurs when a slug of drain water is pushing air in front of it and the air can't escape, that's the purpose of the vent piping, to let air in and out as needed. So the trapped air being pushed exits via the toilet causing the bubbling. That's also the likely reason the toilet doesn't drain properly and repeatedly plugs, the trapped air also slows the toilet solids from moving down the piping causing the solids to slow down and settle out mid-pipe. Then the next flush of solids runs into the first, and from there things spiral into a blockage. The only way to fix the problem is to redo the underfloor piping correctly. If you're on a a slab, that's a huge issue to break up all the concrete and replace the drain piping; you will likely never get the plumber to admit their mistake. If on a crawlspace the fix is much easier. The builder may have sufficient clout to get things fixed but they may balk as well.

I agree that it could be a venting issue - but I'm not nearly as convinced as the person above.

I'm more inclined to believe a buried broken drain or joint that came apart because it wasn't glued properly before it was backfilled. I'm also going to bet that this is on a slab.

Have a company remove the toilet and scope the drain from there first. If that comes back negative, take a good look at the venting (scope it from the roof if you need to).

If it's a broken pipe under the slab, it will be expensive. This is a warranty issue and only becomes the homeowner's problem if they aren't assertive with the builder.

Duplicate post as well https://www.houzz.com/discussions/6432360/new-home-guest-bath-clogs-with-solids-has-dirt-in-bowl-help-please#n=5