Filament tangles on the spool can happen during the winding process. It is not common, but it IS possible. The more common cause is letting the loose end fly free when you change filament. A loop can develop then, which can wind around the spool for quite a long time before it finally binds up.
The only 100% effective ways to mitigate both problems:
Make sure EVERY time you run Unload command you are holding on to the filament as it comes out of the machine and immediately take up the slack onto the spool and attach that free end with a piece of tape or a filament clip (lots of models on thingiverse). I even go one step further and trim that loose end so it is ready for reloading the next time.
When you get new spools from FLUX or anywhere else, as soon as you open them, inspect them thoroughly, check the windings, look to make sure they appear to have a back and forth pattern, and then try to keep an eye on them as you use them. Follow the same procedure as above during use, never let that loose end fly free!
As larger spools (1Kg) get down toward the last 30% or 100m the coil in the filament becomes stronger, this is when you need to do a really thorough re-inspection because if any loop snuck in from a free fly or from a bad manufacturer winding, this is when it is most likely to show up and jam a print. The best thing you can do is to rewind that last third onto an empty spool, it takes a bit of patience and committment, but it is not difficult; or if you do not want to do that, do not start any unattended or overnight prints on that spool. You need to be around to watch that one, consider it as suspect until the spool is finished.
Spool tangles are rare, but they can foul a beautiful print instantly even when you have done everything else perfectly. Just a couple filament handling practices can go a long way to avoid them.