Clogged Basement Sink or Worse?

Hi everyone. I live in MA, have a basement from an incredibly old home, 1890, with gerryrigged plumbing. Everything has been working fine for 1.5 years (first time home buyers).

We noticed some residue coming out of our basement sink in spring, but it didn't happen much. I had someone come over to inspect our water boiler and they said it was likely clogged and recommended I buy an enzyme product to break up the clog. I did this, but it keeps happening, and now it seems to be more frequent.

Today I turned on all of the faucets in my house and waited in my basement until it the sink started to fill up - sure enough water started coming up after like 2 minutes or longer (that including me turning on the shower and darting to every room to turn on each faucet then waiting downstairs).

It looks like mostly dirt, and we continue to get carrots come up - we eat them but I've never even put carrots in the garbage disposal. If I did, it was a year ago, but these were bright orange.

How alarming is this? We already had a professional come in and say it's just a clog but he didn't use a camera we just waited until the sink filled up. I tried getting the enzyme product once. Does this warrant immediate attention or can we try the enzyme a few more times? Also wtf do we have carrots continually when we don't eat carrots? In fact, I don't see anything but carrots. I poured a little bit of the left overs from a French press made with espresso grind coursness coffee and it came back up, but we hardly let anything in the disposal. No grease, either.

Only other thing to note is when the washer and the shower are both on I hear a lot of thuds, sounds like water going through. The guy who inspected our boiler said the water was clean as a whistle, so idk where it's from.