Yes it is possible to add too much puree, curd, nut paste, chocolate, whatever you are adding as flavoring to meringue buttercream; I’ve had it happen and once that emulsion breaks, there’s not a lot you can do to fix it. Because we always have lots of buttercream in the shop, usually I take half of the broken BCRM and add some fresh stuff to it and that helps a lot.
If you noticed some “weeping” with the buttercream when mixing or spreading it, then that would be another indication the emulsion was out of balance.
When we’re working with a cake that has a buttercream finish that I need to “texture” (like stucco or horizontal or vertical lines), I will crumb coat the chilled cake (usually I build a cake and then let it sit in the cooler overnight and crumb coat it the next day) and let that chill for 45 minutes then go over the crumb coat with a second layer of buttercream and chill again. Sometimes I need a third coat, sometimes not. You need to make the lines or stucco before the buttercream firms up obviously but if the room is cold, that can make the buttercream firm up more quickly and throw your timetable off. Or if it is too hot, the buttercream gets very very soft and that is also a challenge. You could also pipe lines on the cake (using a rose tip, and the turntable, to make a horizontal line) and that could help in this case.
Welcome to the forums! Keep baking and telling us about your adventures!!