string to int on return

then continue go up to flooor 6

That's not going to happen.

Kata description says

The Lift never changes direction until there are no more people wanting to get on/off in the direction it is already travelling

There is nobody above floor 4 so the lift won't keep going up...

• Lift started on floor 0 ==> [0]
• Lift goes to floor 2 and 2 people enter (wanting to go to floor 4). ==> [0,2]
• Lift continues up to floor 4. The 2 people in lift get out and 2 people get in wanting to go fo floor 2 ==> [0,2,4]
• There is nobody in floors above 4, so lift takes the occupants to floor 2. ==> [0,2,4,2]
  ... etc

This is not the proper way to raise an issue, and this is most likely not an issue (= a bug in the kata). If really you get different results in your IDE and here, there can be a difference between Java versions, or there is some bug in Java (I seriously doubt it), all o whiwh which CodeWars is obviously not responsible. Please read carefully the documentation: https://docs.codewars.com/training/troubleshooting/

Random test #10: 'pong-ping-pong-ping-boof-bink-doof-ping-smak-bong-ping-pong-ping-pong-ping-pong-ping-pong-ping-pong-flap-funk'. Expected = ping

ping and pong scores are 1 and 2 correctly in my solution.

Wrong.

Kata is correct, because:

• pong-ping-pong-ping-boof-bink-doof- -> pong serves, ping misses; Score ping=0,pong=1
• ping-smak-bong- --> ping serves and misses; Score unchanged
• ping-pong-ping-pong-ping-pong-ping-pong-ping-pong-flap-funk --> ping serves, pong misses; Score ping=1,pong=1

Since final scores are even, "ping" wins because "pong" had the last bad shot.

Your solution is not working if it fails some tests. You should read the description carefully again, there are some important details you may be missing.