Geert Paysafecash lists the gas stations bp, Esso, haan, Shell and Texaco prominently on their Dutch website. Haven't tried it myself but would be a reasonable guess to assume that you'd probably have a better and more consistent top-up experience their when compared to little small shops.
Edit: If you're experiencing issues with partner locations/stores that are shown to be supported on the map by Paysafecash, it's probably a good idea to also complain to support@paysafecash.com (Paysafecash service team) and/or bunq Support about it. The Paysafecash option should be available on the in-store terminals directly next to the Paysafecard option.
