Synth mounting problem

Last week we also did another session of synth mounting. My friend Chris came along to help me since I burned up my own drill last time he brought his. Actually a much better one. Chris is also very precise with measuring and determined the correct positions for all the synth mounts. He also drilled all the 10 mm holes while I was holding the vacuum cleaner. After wards I mounted the synth mounts with the 8 mm bolts. At first glimpse this looked to go alright.

And in the picture on the right you can see the result. We installed four mounts in total. 1 short one just above my Eminent 310 and three long ones on the wall adjacent. When I inspected my work closer I saw that two of the bolts were not completely screwed in. So I applied some more force and unfortunately broke a bolt :( We figured how we could fix this and tried to use a metal drill to get the bolt out, but no luck at all. At that moment we decided to leave it this way. This bolt was on the bottem of the mount where the least force is applied to the bolts. When Chris left I looked again and unfortunately discovered another bolt that was broken :( This time on top.

The day after I called my constructor and asked him for advice. They are coming tomorrow to find a solution. I will keep you posted on this. A little setback but I'm sure we'll find a way to solve this. The cause by the way is that we probably didn't drill the holes deep enough and the bolts were screwed into the concrete.