If I had to guess, not having a shock installed is allowing the spring to extend as far as it can which in turn in over-extending the control arms beyond what they would travel under normal use. So, to answer your question in another way, the shock may be acting as a limiter. On the other hand, a shock shouldn't be used in that way. I'd suspect a grinder would alleviate this issue, but I also don't think you'd ever have the issue with it on the ground or under normal driving conditions.