SharPoint Online Modern Communication Site: fail to create page template, REST error

I’m building a SharePoint online communication site, but when I try to save a page as template or publish a page using defined page templates saved before, it gives me the following error:

REST error Error with code -2147024809, System.ArgumentException due to Inner-Message: Value does not fall within the expected range. Exception-Message: (HTTP):400 - Bad Request (CorrelationId):e3c3a69f-a019-b000-a2dc-4a074ad75594 (Version):16.0.0.20913 at Error: Inner-Message: Value does not fall within the expected range. Exception-Message: (HTTP):400 - Bad Request (CorrelationId):e3c3a69f-a019-b000-a2dc-4a074ad75594 (Version):16.0.0.20913 at new t (https://modern.akamai.odsp.cdn.office.net/files/sp-client/sp-pages-assembly_en-us_6aa2fc520591708ec0b2ff861ee40b72.js:1:329724) at Function.e._getOdataRestApiError (https://modern.akamai.odsp.cdn.office.net/files/sp-client/chunk.sp-pages-statemanager_en-us_e9b99b9a155c33296e29.js:1:20936) at https://modern.akamai.odsp.cdn.office.net/files/sp-client/chunk.sp-pages-statemanager_en-us_e9b99b9a155c33296e29.js:1:23643}

does someone have idea how i can fix this error? Thanks a lot!