I lived in a house in the SF Bay Area, my house had 2-3 areas of cracking, caused by seasonal movement; rain and summer.

About 5 years before I sold, new neighbors brought in soil and raised their property level. Previously, my gutters drained into my side yard, then onto the neighbors yard. After they started using that area, my side yard would have standing water. I put in French drains.

Around the same time, I had the house painted by a painting contractor, they repaired the wall cracks. I never saw them again....sold about 5 years later

Do you have a level or phone app, can you measure the deflection in your floor?

There are SOOOO many reasons for these cracks forming once again....it's hard to say. I would start with the structural engineer. They are the one's who investigate the SAFETY of the HOUSE.

Once they have found the issue, you will want to call back the foundation company (you should still have warranty if you are inside 1 year...it's possible you have 2 years worth of labour warranty but you will have to check your original contract).

I would LOVE to know if the foundation company did any soil testing. And yes, recent builds in your area can and will alter how the earth below YOUR home reacts.

How old is the house?

My house was built in 1943 and I've tried calling the foundation company with no luck when I first noticed the cracks shortly after moving in.

Keep calling them. They probably do not have anyone in the office during this pandemic, it is also possible they may have closed completely (depending on the state you are in). You may need to wait for this to be over and things to open up and back to "normal" (or whatever the new normal will be).

You can assume that the cracks are caused from the pier and beams. If, the cracks are relative to the pier and beam location. Otherwise, it would be seasonal expansion and contracting. Very common in a four season home.

Issue was discovered to be rotted main beam across center of house between kitchen and bath. They replaced beams 2 years ago and I do have a 5 year warranty. Though the main beam was not one of the beams redone so they are saying it isn't covered by the warranty.

Houses in my area are on slabs and we have constant foundation problems. The land was good for growing crops but not so pretty good for housing.

What we have learned is to use a foundation company that has been in business for years and will honor and transfer the warranty to new homeowners. If subsequent work is needed they will adjust a pier for smaller fee than the price for a new one.

BUT only for work they have done. If you have a different company do foundation work, it voids the warranty for the prior work.

Just something to keep in mind as you go forward.

It's the same company but they didn't replace the main beam. Though it should have been because it was the reason for the house getting foundation repair to get my bid on the contract to buy it.

My 2 cents are worth less than that, but I would be raising a big stink about the inadequate repair. That beam didn't rot in just 1 year! Someone dropped the ball.

If you don't have a copy of the contract for the repair, see if you can get in touch with the seller in hopes that they do. The contract may reveal that they should have replaced that main beam if the contract wasn't highly specific about what should be replaced. Was this company the one that determined that the work was needed?