Hey @pico-wrath, welcome to the Rainbow 6 Siege Discussions! I'm sorry to hear about this freezing & crashing you encountered when playing, & understand the inconvenience & frustration caused.
Apologies for the inconvenience, MMR is unable to be granted. For more information, please check out this article. However, I would like to further investigate this freeze & crash you experienced. Would you please clarify if you received an error code or message? Also, have you experienced freezes & crashes for more than this one instance?