We don’t know much about your system specs or what version of IK software you are running here but I use Syntroniks and have used B3X extensively in the past and they never caused crashing on my Windows system.
I’d see if you can run them stand-alone and switch sounds within them stand-alone just to rule out it’s system resources causing the crashing.
Next, I’d try the VST3 versions if you are using VST2 or vice versa. I have always used VST3 versions of these on my windows machine with no issues.
Last thought for now… if you have recently updated and you switch sounds by recalling past saved preset states from within Syntronik or SampleTank, there is a bug I found where it wasn’t reconnecting samples with “multis” which is IK speak for presets and the multi file needs to be edited manually to correct a version number in the file. This sounds unrelated to your crashing but perhaps it’s actually related somehow. Syntronik Not Loading Presets - #12 by brandon
p.s. B3X in particular and SampleTank to a lesser extent are very GPU heavy resources to load. There are a lot of visual intefaces within these plugins and that taxes system resources a bit more than other plugins. Only Arturia’s Mellotron comes to mind as a similar heavy GPU plugin.