Bug introduced in 11.1 and fixed in 12.1
I recently upgraded from Mathematica 10.4 to 12.0. Unfortunately, I am now experiencing crashes with code that was stable in 10.4. The code involves extensive manipulation of the Series function with 2 variables. The culprit seems to be when the logarithm of such a series is taken.
Here is an example:
On Mathematica 10.4, this (rapidly) evaluates to another series in (1/p) and e, while on Mathematica 12.0, it stalls for several seconds and then crashes. Simple workarounds using "Normal" inside the Log and then taking another Series are not ideal, as I need Mathematica to track the appropriate orders automatically, rather than having to set all the orders manually.
Is this a bug, or a side effect of some new functionality? Is there a simple way to achieve the 10.4 behavior?