I set the mk3 personal transformer to 10mw, tried to use a teleport ring with it in my armor grid and got this error:

The mod Personal Transformer2 (1.0.11) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PersonalTransformer2::on_tick (ID 0)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__PersonalTransformer2/control.lua:772: in function 'teleportEntitiesToPlayerPosition'
PersonalTransformer2/control.lua:366: in function 'update_personal_transformer'
PersonalTransformer2/control.lua:342: in function <PersonalTransformer2/control.lua:335>

I'm not familiar with that mod. So, I can only make an educated guess that there may be something finicky with the way teleportation is done. This mod should be able to handle teleportation. Especially since SE uses teleportation a bunch and I tested the mod with all of its uses. If you link the mod page here I can take a look though.

Here you go.

https://mods.factorio.com/mod/transport-ring-teleporter

Other people are also having the same issue it seems. If I had to make a wildly uneducated guess I would assume it has something to do with the fact that the ring is coded as a gigantic accumulator, so its probably fucking with the transformer trying to pull or push energy in and out of it.