This error is normally due to the PicoScope Support Toolbox not being present, this can be added though AddOn manager, just search for "PicoScope Support Toolbox"
The Serial Decoder only pulls down 20MSamples for decoding, the data is downsampled on the device, so even though the device is sampling at 500kSamples/second you won't get that for decoding. The full buffer contains 250MSamples so 20MSamples for decoding means you are getting less than 5 samples pe...
If you select decode between time rulers and then place the cursors as shown, the framing errors disappear. BetweenCursors.png When you enable serial decoding it downsamples data to process, as you have plenty of trace with no data with your settings this results in around 5 samples per bit of the s...
You could save the current waveform rather than the whole set, which may reduce the file size. Otherwise put the file on a file server and send a link to support@picotech.com