I don't know her case, but just recently Taylor Sander retired from indoor volleyball without any word to his club, then didn't respond for weeks to Skra Bełchatów's questions despite having valid contract, and then he played like nothing has happened in FIVB competition on beach, and he's not even an extreme example, it happens regularly on top level (Juantorena or Simon, so best-best players, from the past), because no one cares about valid contracts. Bartosz Kurek lied to his Japanese club that he has mental problems and depression, and needs a break, just to get rid of his contract in Japan, and then signed a contract in Poland and play in Polish league soon after. Imagine something like that in serious sports.
I'll wait for conclusions in Douglas' case until he publicly explains what's going on, but if you leave your club without permission nor explanation (like Vibo Valentia states), with some shit-posting on social media about comeback you're waiting for and announce suprise for his fans <3, then I don't know what the hell does he think.
NG did the similar thing last season at Kazan. He flied back to French to meet his family during X'mas without permission from Club. Kazan had a bad losing streak (lost 5 out of 6 games) at that time. Although NG had a great performance at Tokyo 2021, I won't be his fan coz he's a horrible person on many levels.