DIY repair of a Roger Touchscreen microphone

I have a Roger Touchscreen that is out of warranty. Broadcast range is terrible - the connection becomes intermittent already at about 2 m distance. Transmitter power is set to standard (not reduced). Another Roger Touchscreen mic just works as it should, so I doubt we have a jammed 2.4 GHz band / channel crosstalk issue. Device is otherwise in great shape, battery is healthy. Would love to take a peek inside - maybe it is a simple fix, like a loose antenna flex cable that needs to get reseated in a PCB connector etc., have a feeling the internal antenna does not work. Can anyone advise how the microphone’s case can be opened? I have experience and tools from repairing a few cell phones and consumer electronic devices, but it always helps to have a few tips not to break something.

Would love to get in touch with some DIY repair people in this forum on how to keep all these insanely expensive accessories in shape for a log time without spending $$$.

Thanks!