Cross Margin API behaving strangely

I have 3 accounts. In one specific account only, while fetching account via endpoint /sapi/v1/margin/account the margin api returns this error -

    "code": -1100,
    "msg": "Illegal characters found in a parameter."

It gets auto-fixed within 15 minutes (or more) and api returns correct data thereafter. The other two accounts face no such issue. This problem appeared first 2 days ago and is now repeatedly affecting my trading. I have been API-trading since more than a year without any issues until now

Above image is a snapshot of terminal running code to fetch margin balances via api - (code unchanged between the multiple executions). As you can see, it gives the error and gets auto-fixed after 4 minutes. I have tried postman. It gave the same response.

UPDATE: Even the UI is not showing the margin balances.

Please have a try with this python example code, which will print parameters and request in the log.
If you could reproduce, please share the log here. Mask the sensitive info like you did above.

thank you.

Even the UI is not showing margin balances while it continues to show isolated and spot balances. This is surely a binance-side issue for my specific account

this seems an issue that happens on your account, please feel free to contact customer support, they may help to check the account details.