Now full swing appears to be 0xF7 without changing anything else, so is this a late-night typo?
Thanks for the quick reply, I've tried turning DTR off and shorting the RST pin to the GND pin with a 10uF capacitor as stated in the serial auto reset disable guide but those didn't help either. What confuses me is that this doesn't happen at all with my uno v3 which also has optiboot installed.
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