Use a better silicon(e)?

Can you take a picture of what you are talking about and post it? I'm guessing it may be something other than caulk (maybe grout) but without a picture, it's hard to tell. You can post a picture by using imgur.com and adding a link to your post/comment.

Sounds to me like the cabinet is not fixed securely.

Movement is what causes cracks in silicone sealant.

Sounds like it needs maybe an L bracket or two, then re silicone

Is the gap changing? Are the cabinets pulling away from the wall? If the gap is staying the same, get a more flexible caulk.

Any brand recs?

I also wonder if the cabinet installation didn’t factor in the weight of the cabinet contents.

Unfortunately, your new house is settling so cracks in mouldings and fixtures will be quite common for a few months to a year. Just ignore it for now or use it as time to practice cutting it out and redoing it cleanly.

Scrape it out, and reapply DAP kitchen and bath silicone of the color of your choice. There's endless tutorials and tips out there on YouTube and other platforms on how to actually do it.

Silicone will shrink as it dries, so make sure to squeeze it back into the gap. Another possibility for why it cracked was if they used grout instead of caulk. Grout is hard and shouldn't go against a wall, but there's mixed opinions on that, but grout on walls always cracks eventually.

Seems the same. I’ll keep monitoring.

How can I measure/determine caulk flexibility?

I think you’re onto something. To have this happen repeatedly seems like a support problem.

Good caulk doesn't crack. They either used grout (super hard, should only be used for butt joints) or painters caulk (super cheap, should be used for interior painted surfaces)

Go buy some good caulk. Cut the old stuff out and redo.

That’s a good point too. I can be patient and get some caulk reps on my résumé!

Post a picture and I'll give some further advice

Any brand recs for good caulk?

The caulk you want is Dap Dynaflex 230. Very flexible and easy to work with, sold at Home Depot.

I'm not a fan of 230. It skins over fast and is tough to tool. I'd consider it premium painter caulk.

For a kitchen bath buy real silicone. It's going to be $10

DAP

Homeowner of many years & worked for a builder—have recaulked most of my house. It is pretty easy & I think it’s fun. Definitely watch a few tutorials. Makes such a huge difference when you refresh the area. As poster above said there is a LOT of movement in a house the first year or so, perfectly normal. What you need to be wary about is cracks that seem out of place. Just call the builder/contractor & ask or send a pic if you are unsure.

DAP is the stock standard good option. That said I’ve switched out to GE’s Advanced recently as I like how it applies a bit better, but either option is great.

I have had better success with the stuff that has longer dry times. You just need to research the different brands. Sherwin Williams had a really good one, but it is not the same post pandemic.

I'm betting it's grout as well. Seen that too many times between horizontal and vertical surface. Caulk always.

DAP Extreme Stretch is pretty good.

DAP is great. Alex plus is good as well; that's what I use when I professionally remodel bathrooms and kitchens.

Is it a stone counter top ?

Clean it really good and then lay down green tape exactly where you want the caulk lines to be, push it down really good, then lay good caulk and smooth it with your finger so it looks smooth and doesn't show anything beneath it. Pull the tape off before the caulk sets, pulling it in a way that it doesn't touch anything. This gives a really great line.

Big stretch I've also had success with. Just another option in case availability at your local store is limited

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Learn how to caulk with the noiseless cut square, not diagonal, and run the opposite direction you're used to, steady hands, pushing whatever product you get out into the gap with the rounded edge of the nuzzle shaping your beadninstead of mashing it with your finger

What about big stretch from Lowe’s?

Learn how to caulk with the noiseless cut square, not diagonal, and run the opposite direction you're used to, steady hands, pushing whatever product you get out into the gap with the rounded edge of the nuzzle shaping your beadninstead of mashing it with your finger

Wet your finger first.

I always use silicone. We used it at work all the time. Wet your finger when smoothing it out.

Could be the color matched unsanded caulk if there is grout nearby. It’s not as bad as cheap painters caulk, but isn’t great either.

Geocel is by far the best caulk. I've done residing jobs on 40-50 year old siding that had Geocel and it still has to be peeled off in one solid line or cut down the middle.