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BLE works at 2.4GHz and sends very small packets.
Everything is running on the same processor. So, there is a good chance to interfere with the radio. In general you should write your code so loop runs as often as possible, no delay or waiting for stuff to happen ... then you should be fine.
What are you doing in that handler and how often does it run? Short interrupts should be fine but spending a lot of time in there is generally not a good idea.