multiple tables on one template

When I render two or more tables on same template I get several deprecations like this one

DEPRECATION: You modified (mut bodyContent) twice in a single render. This was unreliable in Ember 1.x and will be removed in Ember 2.0 [deprecation id: ember-views.render-double-modify]

Furthermore, tables are loading very slow, they are buggy and unreliable - most of the time tables are populated with data, but it even happens that they stay empty - like there is a race condition problem.

Does anyone have an idea what could be a problem?