For the advises which you have given:
1- I am running sympy 1.5.1 so I guess it is a recent version.
2- I will try to report it on its github project once I find some free time.
For comparison, I was able to get the result instantly while using MATLAB
from my University's Computer Lab.
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Sent from: https://octave.1599824.n4.nabble.com/Octave-General-f1599825.html
I got it to work
First let me say that it ran here for more that 10 hrs. as you presented it. But no error.
If you do ilaplace(partfrac(aux.i2))
then you will get the answer within 1 minute.
What this does is help the solver by doing the partial fraction expansion first.
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DAS