Clarification on Canon 188

There is currently controversy between some Catholics regarding the current pope and the validity of him holding the office. On a video addressing this controversy (which I can no longer find), a comment mentioned that some people believed the current pope to be invalid due to Canon 188 in Title IX of the code of the canon law: Can. 188 A resignation made out of grave fear that is inflicted unjustly or out of malice, substantial error, or simony is invalid by the law itself. My question is, what exactly is this Canon saying, especially with regards to the "substantial error", and how are people interpreting this to apply to the current pope?