TWI/I2C hardware in AVR is byte oriented so only if master succeeded to transfer a byte and received an ack/no-ack from slave then
a transaction is consider successfull/valid.
If you deal with AVR as slave device, only valid transaction will trigger slave interrupt routine.
TWI/I2C transaction depends on synchronization of SDA and SCL pulse. Once those pulse become un-sync then the TWI/I2C comms will "hang" or
"freeze" which can cause your MCU to freeze if you aren't properly handle it.
Handling this situation commonly with disabling the TWI/I2C hardware and wait for some amount of time then restart over.
So if you had experienced how to disable and restart TWI/I2C hardware then this experiment is not for your interest.
If you're electronics hobbyist and interested to know what's going on then follow this step by step experiment.
Usually engineer or hobbyist own Logic Analyser and Oscilloscope to trace their problem.
This is the simple and tricky way for them who don't own that expensive equipment to experiment.