hello, we were just reported about incompatiblity with istraxx customsize plugin which requires a modification to be compatible with any system which gets checkout prices more than once per request (for example if you got a mini cart module enabled and you are at the checkout page, the plugin will get executed twice)
when used with our OPC which pre-calculates the shipping/payment combination and thus calls the getCheckoutPrices multiple times per request, this plugin will not return proper values at all.
please update your function in :
\plugins\vmcustom\istraxx_customsize\istraxx_customsize.php
(see code below)
best regards, stan