It is well-known within the community that Mirza Mahmud had a very volatile temper in the last 10 years of his life (1955-65), and was almost continuously bedridden, had bouts of searing pain, and had other serious problems with his personality and mental health in general. His biography on Wikipedia contains he following:
After recovering partially, he traveled to Europe for further medical and surgical treatment due to constant discomfort and unease. Briefly staying in Lebanon, Mahmood Ahmad travelled to Switzerland via Athens and Rome. He continued travelling and received some medical treatment in Zurich, Hamburg and London. After consulting with his doctors, it was concluded by that the tip of the knife had broken and embedded itself in the jugular vein and that no attempt should be made to remove it.As more facts come to light, this official story seems less and less likely, as any tip of the knife would have been visible in X-rays and he should have gone to Lahore or Karachi for more diagnostics. Also, why did he visit so many cities for such a straightforward issue? And a 'metal tip in the jugular vein' could be removed and would only have caused physical pain instead of interrupting his writing and speaking career.
He also lost overall command of the Jamaat, resulting in his sons Mirza Nasir, Munawwar and others becoming very powerful. This lack of command resulted in the ungrounded Mirza Nasir becoming Khalifa after his death and led to misguided policies and political adventures that resulted in Ahmadis being declared non-Muslim for purposes of the law in Pakistan. After analyzing the excerpts below, the Lahori version of his illness is more believable: that he suffered from neurosyphilis towards the end of his life. That would explain the official as well as the rumoured symptoms.