I do not have LPC1768 so I do not know, but is popular target so I believe potential issues would be already reported here or on github.
I see just this
Mbed CLI 1 - Mbed OS 6.4 and older
Mbed CLI 2 - Mbed OS 6.5 and newer
About interrupt in general the Mbed OS 5.12 was game changer because all methods what have potential with manipulation through threads are covered by Mutex and mutex can not be used in ISR - read / write / printf / send / received and os on
Did you firmware updare of your LPC1768? That could be the magic.
BR, Jan