How long the curse of bad education remains in academic career?
From a European perspective: the only time I was ever asked for transcripts was for PhD admission. After that, nobody every asked me for transcripts.


Administrative people asked me for a proof of my degree (a copy of the degree itself, without grades, is what I gave). They only wanted to check I was eligible for the position's formal requirements (having a PhD to become post-doc or assistant professor).
Scientists asked me for my publications, my thesis, the list of topics I had taught, etc. They did not care the least about my grades in undergrad or graduate education.


So, I think the ads you saw asking for transcripts, especially for senior positions, are by far a minority. Once you have a PhD, most people won't care about your earlier educational record, since it is not a good predictor of how awesome you will be as a researcher.