Welcome Sneaker!
I haven't heard of that problem, but I found this in the bug tracker:
https://bugs.launchpad.net/inkscape/+bug/1418865. It doesn't sound like exactly the same thing to me. This report seems to apply to 100% transparent objects, not partially transparent. But it still could be related (for all I know).
And there's also this report:
https://bugs.launchpad.net/inkscape/+bug/1425393. You didn't say which settings you used.
You could post a comment to whichever one of those bugs seems to be the most appropriate. And if the developers think it should be a separate report, they'll ask you to make one. Or if you make a new report, and it turns out to be related to other bugs, they'll mark it to indicate that.
Or you're welcome to search the bug tracker yourself, as well. You may be able to find other similar bugs. Tbh, I've had an extremely poor experience with the Launchpad search. I've searched for bug reports that I know exist, with words which appear in the title of the report, and the LP search doesn't find them! So if you know how to search without using LP, you might find other reports. (I can never remember how
)