Air 31 Standard packaging for iOS gives Compile error

I have a AIR app that needs updating for the iOS 12 issues.

It is built in Flash Builder 4.7

When I build with "Fast" packaging it installs and runs fine.

When I build for production (to send off to Apple) or "Standard" packaging I get a error

"

Instruction does not dominate all uses!

  %"str:None" = call %"avmplus::String"* @llGetString(%"avmplus::PoolObject"* %pool, i32 34)

  %"str:None_cast6" = bitcast %"avmplus::String"* %"str:None" to i8*

LLVM ERROR: Broken function found, compilation aborted!

"

Anyone seen this error and know how to fix it?