@puiradu

when you update on the blcak-plastic theme, a warning banner appears like this:

"the theme has been set to default, go to menu, settings, plastic theme settings to set-up the theme"

(i do not know if i got it word-by-word but i think i got what that means)

it means, in the update, the theme is de-activated and then you need to set it up again. this reason, i believe, is that a reboot is needed for the theme changes to take effect.

i am using most of D-Iivil's themes, and i am always told by the description to re-select/set-up the theme and reboot. which means, your theme will be set as default and you just need to re-activate your desired theme and i believe is NORMAL.

EDIT: if i am wrong, try re-selecting other themes, and wait for 5 mins, if the theme still is the default, nokia n-series, and needed a reboot, this maybe a bug on changing themes.