Hi,
I’ve done a bit more digging and the error is on the json sent to Paypal.
I think its this file
wp-express-checkout\assets\js\public.js (and the min version)
line 279 and 289 are outputting a “value” field to the json but its not rounding the value to 2 decimal places (as I need).
I’ve testing it by using Math.round and it works but I’m aware this won’t be suitable fix as it doesn’t take into account the decimal setting in the plugin admin.
But I hope this helps tracking down the issue!?