How to fix water leak between tub and shower walls
I would avoid caulking again as it's likley to become a re-occuring problem, it's best to fix the source issue.

Contact the original contractor, they may repair the work if it's under warranty.

If they are unwilling, check with your local regulations as your original contractor may be liable for repairs, certainly seems like a fault with the original installation.

Home insurance may also cover you for repairs, if you are insured contact your agent even if only to register a case number early on in case it blows up to something that will need coverage.

If you are stuck without any of those options and don't want to overspend, there are companies that specialise in sealing bathrooms over tiles/panels using specialised  sealents, you should be able to find one that will do the job for under $200/$300 - ensure they provide at least year warranty. Google 'over tile waterproofing'.