May I know the data size in platform_uart_receive_bytes()? Also let me know the ring buffer size that you are using. I could not reproduce this issue using the values specified in snip.uart.
Read this thread then you should be able to understand the *problem*.
If you search the forum with keyword "uart received timeout" you
will find a lot of issues reported for years.
I even tried to leave a message mentined it's a sdk bug in some report.
Somehow, cypress keep ignore the bug report on the forum.
typical requested bytes for this is 1.