The worst part of this is if you wait more than 10 days after 1709 is forced on you, it won't let you go back to version 1703 (which wasn't locking up the computer). I didn't even know that 1709 was loaded on this laptop, but I noticed the constant crashing (nothing works, not even the keyboard or mouse so you can't get to the task manager) and finally figured out that my computer was updated behind my back. Fortunately I have an old W10 backup on hard drive, but I'm going to lose many of my documents and programs if I restore it. So now I'm caught between a rock and a hard place. Thanks Microsoft!
Probably worth trying the "disable fast startup" fix - and also make sure you have got all available Windows Updates (if the computer runs enough to be able to do that).
The fact that you can get task manager up tells me its not the exact same problem I have. When mine freezes its total game over until a reset. However, many people have reported that an early March Win Update solved their problems.
As for the docs you have, copy them onto a memory stick or sync them to OneDrive. If the laptop won't run at all, maybe start it in safe mode to enable you to copy docs off. As a last resort, remove the hard drive and connect it to a different PC to get the docs off.
Hope you find some solution.