I had some issue on my 1st try ever. and yea i broke tap root on 3 of my 8 seedlings.
I do a mistake and leave them too long in paper towel so the main root drove directly
through several layers of paper, and when I tried to gently pull out was broken..
Yea newbie can do this kind of mistake, like i do but never happen agin to me.
Im using different method now, with 100% results...
I just soak beans 12h-24h (or till the shell crack) in tap water, when that happen you can see the white slot through one side of the seed. Such seed can safely put continue to germinate in any substrat ...
Rockwool,root riot,coco,perlite,lava rock,clay beans, soil.... all except soil need Ph-ed water 5.5-6.0.
Last grow i start using 1/4 str. of Rhizotonic with good results...