This was describe by Marry Walker (the woman physician who discovered neostigmine/mestinon). In fact from this clinical observation she concluded that "the paralysis in myasthenia must be due to a positive toxic substance produced in the course of muscular activity"

Surprisingly, modern MG experts (including those considered leaders in the field) are not aware of this, and have never seen this before. Or possibly they did, and just called it "collapse like episodes" as a result of some ill-defined emotional problems. (like one leading expert I have encountered).

To me this means that your MG is taking its natural course and is not under good control , so you need more aggressive treatment.

Also, make sure they check the levels of potassium. Low levels of potassium are easy to correct, and can lead to worsening of MG.