Targeting mode is broken on author instance

[#1]

Hello Adobe Community,

AEM 6.3:

We have an unexpected issue on one of the instances when you switch to target mode:

-error in the console

-"start targeting" button is disabled

-no activities and brands.
Page is broken here on doctype html:

Could you suggest please what it can be?

Thanks.

[#2]

Hello once again.

The problem was trivial... no "jcr:content" node under our brand.

Thanks.