Issues with 64bit VST

I've lately been encountering an issue that I cannot understand. I'm working on an effect plugin, and for a while it runs just fine. I use it on my Windows 10 PC, as a 64bit VST, and test it out on a newish version of Reaper, and sometimes on Ableton Live 9. But then, I work on it some more and suddenly it crashes both DAWs. I initially assume I've made some kind of mistake and try methodically commenting out the code until its just a bare shell but it makes no difference. Then I uncomment everything, and try it as a 32bit VST and everything works again. This happened yesterday. At that point, I decided to just start a new project and copy all the code across. Strangely, the 64bit VST was working again. But today it's crashing both DAWs again, but 32bit works on both DAWs. I wish I could figure it out, but I have no idea.

I'm using the latest version of JUCE Introjucer and am using the Visual Studio Professional 2015.

After looking more closely at my code I realise that this time around, I did make an error with a pointer. Though it is strange that such a bug should only crash a 64bit plugin and not a 32bit one.

Not strange at all! Pointer errors can do some very random things.