Yes, these are the obvious artifacts of flare. But there also is a less obvious effect of flare, when flare is evenly shed across the entire negative.
If you use a fixed focal lens and stop down sufficiently, you won`t get flare in direct sunlight with a mc lens. But i wanted to point out that you even can get flare with a mc lens, because every lens does produce flare. You won`t notice all the time but every lens does, even mc lenses.
I`m sorry but also you suffer flare with your enlarger. If you could have your glass carriers and condenser lenses multicoated, you had higher contrast prints all the time - as the optical elements in your enlarger also do produce flare and by that reduce contrast on the print.
Of course glass carriers are used for film flatness, but they also do reduce contrast on the print because they produce flare - which is why some use glass-less carriers, though these cannot hold film flat.
Best Regards,