It is a complicated issue as it is with every large update. I don't know if they some problems like Bitcoin and Bitcoin Cash back then? But I would not know why that could be the case.
Whatever but these updates are probably discussed in the slightest detail and I am sure there is no consensus all the time between them. Especially if you consider that the development individually has money at stake, which is good for the community but also leads to discussions because all of those brilliant minds on the Ethereum development team has their own opinion.
But they can do so much testing that t should be relatively safe. There have been other forks although this is of course a huge one where all players have to agree. It should go well and hopefully have good effects.