The new touch control has 3 to 5 buttons in the top right corner, and it's really practical that they're placed there. But there is also the potion effects tab in the top right corner, and with 2 or more potion effects it overrides the jump button, making it only usable again when the potion effects run out.

This issue can easily be fixed by changing the potion tab to the left when using the joystick control

Example video:

https://drive.google.com/file/d/1kKzZZn2wPZOd3XNbnuV-3QzlmfNE0tzh/view?usp=drivesdk