How to properly split grounds
Pending an answer to my comment, I suggest you do not over think things and just make sure high power current return paths don't coincide with digital logic and other return paths, since ground current  is the primary issue at hand for most ground related device failures  (inductive coupling ), it should be relatively straight forward to determine where the highest current return is and focus efforts on those first, before a major redesign of the whole ground network.
Split ground is somewhat of a nuclear option , but logically classing and routing  different signal returns is a good idea.
Ground coupling issues are categorized as typically inductive and capacitative, most people have enough good sense to make ground connections fat and low resistance.
Inductive coupling is associated with high current mixed sysyems, What happens is these produce voltage spikes on the ground net that impact all devices further up the ground chain, here star grounds are a popular solution, every &quot;arm&quot; of the star is inductively decoupled .

Source:Analog Devices MT-031
See also: https://www.ti.com/lit/slyt499