Permalink problem

I have come across a strange problem

I am not able to save a page containing the Vendors Dashboard shortcode unless I have permalinks set to PLAIN, i get the message ‘update failed’ on a pink bar

I am likewise not able to view that page unless the permalink is set to PLAIN, otherwise it says PAGE NOT FOUND (the page above exists which is why i can try to view it but i am no longer able to edit it and save the new content)

Additionally, if i disable all plugins and only have woocommerce and wc vendor active, then i cannot save the page mentioned above

And if i disable wc vendor and only have woocommerce active, then i am able to save that page

Any body come across this problem and how to resolve it?

thank you in advance

Serge