The oversampling should be set according to the SCB clock period as well as the data rate. The relation between the SCB clock period and the baud rate is given by the formula (Tdata = TClock * oversampling factor). If you are using internal clock PSoC automatically derives the clock accordingly. Please share the screenshots showing the error when you are configured oversampling as 16. Also if possible please probe the UART lines and attach the screenshots.
I can't easily attach a probe to the UART by now, there is no test points for UART lines in our PCB
some of the incorrect received values (typical error is: first 2 bytes has wrong value and 1 byte missing)
the expected correct value (after a re transmit request)
uart configured with oversampling=16 (error occurs):
uart configured with oversampling=8 (no errors):
UART advanced configuration (same for both oversamplig set to 8 and 16):
I would like to reproduce the issue at our side. Please attach the project in this thread.