You've got data coming in at 4800 baud, and data going out a 38400.

So you can send 8 bytes in the time it takes to receive 1 byte.
The USART has a 2 byte buffer, so you can only send 16 bytes (or less) to the PC without expecting to see overflows.

But, In this statement...

serout2 test,BAUD,["BUFFER=",HEX BUFFER[0],",",HEX BUFFER[1],",",HEX BUFFER[2],",",HEX BUFFER[3],","
,HEX BUFFER[4],",",HEX BUFFER[5],",",HEX BUFFER[6],",",HEX BUFFER[7],10,13] 'JUST CHECK 1ST 2 VALUES

depending on the values of the data, it will send up to 33 bytes.

Since you are using ON INTERRUPT, the next interrupt can't happen untill the serout2 statement has finished.
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