Strange labels with suffix -0, -1 in jmeter results

Question

We recently updated apache jmeter from v4.0 to the latest v5.4.3.

The tests are running fine, but we have strange results. The requests appear with 3 different labels (without suffix or -0 / -1 appended).

timeStamp,     label,      responseCode, threadName
1643834640785, API call,   200,          Load Group 1 1-1
1643834640785, API call-0, 302,          Load Group 1 1-1
1643834641189, API call-1, 200,          Load Group 1 1-1
1643834640785, API call,   200,          Load Group 1 1-2
....

It seems to me this happens, when the same thread calls the API multiple times.

I am not a jmeter and I am not sure why this happens and how to fix it. Also I don't know what information is needed to analyze the problem correctly.

Thanks in advance!