Poking & peeking the same sample should be possible, though the order is obviously important. You can make the order explicit within genexpr code, but not in a patcher. But as Max says, it really depends on what you're trying to achieve, and it may be that a history op is the easier solution.
In any case it shouldn't cause a crash. If you can make a *minimal* example (as simple a patch as possible, no externals, include any needed subpatchers) that triggers the crash, please send it along to email@example.com and we'll take a look!