sharepoint templates

hey guys, i have the follwoing problem, when i want to use a MICROSSOFT template:

"After parsing a value an unexpected character was encountered: V. Path '[17].imageAltText', line 421, position 51."

and, its not only in my tenant, i get the same problem in another tenant too.

the support-team doesn react and that just keeps me from working since tuesday.

any suggestions how to fix that?