Show me a contract where an LP gets to renege penalty free on their obligations to a VC and I'll be happy to believe you.
I have been part of 222 VC/PE deals to date (that's not a typo, just a coincidence) and not once has an LP reneged on their obligation to honor a capital call without penalty. That's not saying it doesn't happen, it may well happen, or it may have happened and it was kept so quiet that nobody picked up on it (which is somewhat believable, because it would reflect very badly on the fund).
Just to give you one example: a VC enters into a deal, signs a non-binding terms sheet conditional on doing DD, goes through a full DD and then has to back out of the deal because a large LP does not honor their commitment. The fall out from that would be massive.
What is far more likely to happen is that a VC can't find a good way to spend the funds committed capital. In that case there might be extensions of the funds run or they might end up simply not calling up the available capital. This I've seen a couple of times. But an LP that refuses a capital call I've yet to see. I've even seen an estate that was held to perform when an LP ended up with the very best reason for non-performance of all.