Our problem seems to be on both Rx and Tx. Scope trace shows timing is about right but 1.5% difference in timing is not easily measurable.For the protocol we're using, when the 1st stop bit goes high we're sometimes reading that as the leading bit (=...

We seem to be having a similar issue on an STM32F427, we have to adjust our BR up by about 1.5% to get reliable comms. No framing errors or noise flags set, it's just identifying the first stop bit as a data bit, like the sampling is lagging behind. ...