Hello,
The .aspx extension should work for every page even with extensionless setup, when "aspx" is not mentioned in settings.
Could you please describe how exactly do you specify the extensions in
Site manager -> Settings -> URLs and SEO ->Friendly URL extensions?
Could you please try to use ";;.aspx" if you don't use that already?
Thank you in advance for information.
Kind regards,
Zdenek C.