In Lens there's a suggestion system enabled by default until 7.17:
Because suggestions are always rendered quite often on changes made in the configuration, this can take up some time especially for Over Time suggestion. In recent releases some performance tuning have been introduced in order to discard the Over time suggestion in some heavy scenarios, or disable altogether the suggestions system:
In 7.14 the only option I think you may have is for metric columns with formula to use them and enable the fullscreen in formula: this is the only case when suggestions are disabled in older versions.