Issue when fetching isolated margin transfer


I am trying to fetch my transfers history for isolated margin symbols.
Using postman and this endpoint, I am able to successfully to fetch my transfers for BTCBUSD and ENJBUSD (all of them are less than a month old).
However when I want to fetch my transfers for KAVAUSDT which were made in 2020/06, I only get an empty list as a return.
Here are the parameter used:

    'symbol': 'KAVAUSDT',
    'startTime': 1591228800000,  # 2020/06/4
    'endTime': 1591747200000  # 2020/06/10

Is it because the transfers are too old?
Thanks a lot

What is the transfer direction you expected to see for KAVAUSDT (SPOT to ISOLATED_MARGIN or the opposite) in 2020/06?
Just to make sure, you can request with “transFrom” and "transTo”, besides having ‘startTime’ and ‘endTime’ for whole the whole 2020/06 month.

I expect both of them, in total about 10 transfers in 2020/06.
transFrom and transTo are optional args, so even without providing them, I should get a return

any pointers on this issue? I really don’t get why the behaviour is different