debugging DrawBuffers crash on older iOS devices

Hi all,

I'm experiencing a crash that I'm having difficulty debugging. I'm using Unity 5.3.7.

It only occurs on older iOS devices (ie devices not running the Metal graphics API).

In the xcode log the crash occurs here:

Thread 1 / DrawBuffers()

at this point:

0x1765262 <+514>: bl 0x1759594 ; :Image may be NSFW.
Clik here to view.rawElements() at ApiGLES.cpp:461

this line -> 0x1765266 <+518>: b 0x176527e ; <+542> at GfxDeviceGLES.cpp:1506

The error message is

Thread 1:...

debugging DrawBuffers crash on older iOS devices