Modification class issue

Hi,

I’am an Oxygen user and, in different website, I have always the same problem:

• When I try to modify a class in Oxygen Builder and then save it, the system add a lot of times the same class (image 1 in attachment);
• Or I can’t see the class inside the Oxygen panel (and modify o remove the class) (image 2 in attachment)
• When I click on the element I would be to modify the class (i.e. div_block-123-43), I have the error in image 3 in attachment.

I have written to Oxygen Support and they say that the issue come from Oxygen Extension.

Do you have had this issue other times?

Can you help me to solve this issue?

I.E. 

page: https://geicolors.com/prodotti/

You can understand how difficult it is to work like this. I am a web agency and this problem (also present on other sites) is a big problem for me.

Thanks

Randall