TECHNICAL ERROR: unable to save update quantity Details: Error thrown: [object Object] Text status: parsererror

[Mat22]

The error shows up with a plus or a minus when increasing or decreasing the quantity, but what I found in another forum does not help, i.e. disabling bug reporting. The bug still exists. The error can be eliminated by turning off the PayPal module, but I need PayPal and I don't want to turn it off.

Presta 1.6.1.24
https://www.discountpolonais.fr/