I'm currently reading through a book that pretty thoroughly eviscerates that last point as a myth. Part of the argument is that he was resistant to efforts to b

I'm currently reading through a book that pretty thoroughly eviscerates that last point as a myth. Part of the argument is that he was resistant to efforts to bring classical concepts into the new domain, thinking that something entirely new may be needed to explain reality. He also spent a lot of time (naturally) trying to square it with GR, something we're still working on today. He kept up with the math and the experiments, but took a contrary view on the interpretation. As an interesting side note, the Copenhagen interpretation which was emerging around that time is now disfavored by the wider physics community (except as a calculation tool).