32bit device only crash on iOS - ios

Question

I'm receiving crash logs for a bug that I cannot reproduce. The crash only happens on 32bit devices (iPad 4, 3, iPad Mini) so I believe that is a major part of the issue.
The crash occurs on the audio thread, while calculating coefficients for a filter. The filter is composed of a C struct and related functions... once I had an issue with needing to align structs correctly for 32-bit devices, but I'm not sure that's the case here (and I'm not sure how I would test that!)
Beyond that, I'm stumped. Here are the first couple lines of the function in which it crashes. The cos function is the second to last frame of the crash log.
void _calculateWithoutUpdatingSetup(ONCBiquadFilter * filter) {
if (filter->res < 0.01) filter->res = 0.01;
filter->omega = 2 * M_PI * filter->freq / sampleRate;
filter->omegaS = sin(filter->omega);
filter->omegaC = cos(filter->omega);
filter->alpha = filter->omegaS / (2 * filter->res);
///... do a bunch of maths to calculate filter settings
}
And here's the crash log :
18
Crashed: AURemoteIO::IOThread
EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000000
Crashed: AURemoteIO::IOThread
0 myFramework 0x41077a _calculateWithoutUpdatingSetup + 2417
1 libsystem_m.dylib 0x20b229d8 cos + 584
2 myFramework 0x40fa2f ONCBiquadFilterCalculateCoefficients + 14
3 myFramework 0x40fd03 ONCBiquadFilterSetFrequencyAndResonance + 214
4 myFramework 0x414c7b ONCAterotVoiceSetFilterCutoffAndResonance + 206
5 myFramework 0x407677 ONCAterotPolyVoicePlay + 452
6 myFramework 0x3e0d61 ONCAterotLoopStructTick + 1092
7 myApp 0x21333 DSPRenderCallback (ONCAterotAudioController+AudioRenderCallbacks.m:367)
8 myApp 0x20b0f renderCallback (ONCAterotAudioController+AudioRenderCallbacks.m:73)
9 AudioToolbox 0x233224b3 AUInputElement::PullInput(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long) + 126
10 AudioToolbox 0x234379ab AUMatrixMixer::Render(unsigned long&, AudioTimeStamp const&, unsigned long) + 554
11 AudioToolbox 0x234385a5 AUMatrixMixer::RenderBus(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long) + 104
12 AudioToolbox 0x23227d01 AUBase::DoRenderBus(unsigned long&, AudioTimeStamp const&, unsigned long, AUOutputElement*, unsigned long, AudioBufferList&) + 148
13 AudioToolbox 0x23227b91 AUBase::DoRender(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long, AudioBufferList&) + 740
14 AudioToolbox 0x232278a3 AUMethodRender(void*, unsigned long*, AudioTimeStamp const*, unsigned long, unsigned long, AudioBufferList*) + 46
15 myApp 0x65d29 eqCallBack (ONCAterotAudioController+effectCallbacks.m:110)
16 AudioToolbox 0x233224b3 AUInputElement::PullInput(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long) + 126
17 AudioToolbox 0x233f21b1 AUDynamicsProcessor::Render(unsigned long&, AudioTimeStamp const&, unsigned long) + 308
18 AudioToolbox 0x23227d01 AUBase::DoRenderBus(unsigned long&, AudioTimeStamp const&, unsigned long, AUOutputElement*, unsigned long, AudioBufferList&) + 148
19 AudioToolbox 0x23227b91 AUBase::DoRender(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long, AudioBufferList&) + 740
20 AudioToolbox 0x232278a3 AUMethodRender(void*, unsigned long*, AudioTimeStamp const*, unsigned long, unsigned long, AudioBufferList*) + 46
21 AudioToolbox 0x23318d89 AUConverterBase::RenderBus(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long) + 396
22 AudioToolbox 0x23227d01 AUBase::DoRenderBus(unsigned long&, AudioTimeStamp const&, unsigned long, AUOutputElement*, unsigned long, AudioBufferList&) + 148
23 AudioToolbox 0x23227b91 AUBase::DoRender(unsigned long&, AudioTimeStamp const&, unsigned long, unsigned long, AudioBufferList&) + 740
24 AudioToolbox 0x2330864b AURemoteIO::PerformIO(unsigned long, unsigned int, unsigned int, AudioTimeStamp const&, AudioTimeStamp const&, AudioBufferList const*, AudioBufferList*, int&) + 506
25 AudioToolbox 0x23309851 AURIOCallbackReceiver_PerformIO + 596
26 AudioToolbox 0x232ff67b _XPerformIO + 166
27 AudioToolbox 0x23245d69 mshMIGPerform + 184
28 AudioToolbox 0x232d6533 MSHMIGDispatchMessage + 34
29 AudioToolbox 0x23308973 AURemoteIO::IOThread::Run() + 118
30 AudioToolbox 0x2330c331 AURemoteIO::IOThread::Entry(void*) + 8
31 AudioToolbox 0x232238db CAPThread::Entry(CAPThread*) + 186
32 libsystem_pthread.dylib 0x20bbcc7f _pthread_body + 138
33 libsystem_pthread.dylib 0x20bbcbf3 _pthread_start + 110
34 libsystem_pthread.dylib 0x20bbaa08 thread_start + 8
Thanks for any guidance in solving this!
Update : I did notice a couple of mistakes on my part -- freq, res, and sampleRate are all floats, while the rest of the values are doubles. I could see this maybe being part of the issue, though I sort of doubt it as they should just be getting promoted into doubles.