I also have had similar behaviour before now when running multiple tests in sequence certain ones failed whereas if I ran the tests individually the tests passed.
This issue was nearly always due to resourcing and latency when I had this issue.
As HimanshuTayal suggests - you need to review your logs but maybe provide a bit more info.
Did the same testcases fail each time or were the failing testcases different?
The reason for the failing testcases - are they failing on particular test steps? e.g. JDBC request to retrieve a large number of records?
The latency could be local to you (your laptop resourcing) or server end resourcing (threading/memory/CPU resourcing).
To 'fix' my problem, I added some waits via the 'Delay' test step at appropriate places (within my tests within the project) just to slow things down a little (based on the results of my analysis of the failures) and this resolved my problem.
I also checked that I wasn't running the tests in parallel but in sequence which can cause different tests to fail each run depending on the available resourcing for the endpoint I was hitting.