Recompilation results in linking failure or program segfault

Summary

I have a small program (one newtype, one class, one instance) that seems to mess with recompilation. If I make a minor change to the source and recompile, linking will fail. However, adding a little more code (namely, a composition with id) results in successful compilation, but SIGSEGV in runtime, when a certain thunk is evaluated. It is worth noting, that -O1 makes the issue go away.

(lldb) target create "./Main2"
Current executable set to './Main2' (x86_64).
(lldb) r
Process 22932 launched: './Main2' (x86_64)
Process 22932 stopped
* thread #1, name = 'Main2', stop reason = signal SIGSEGV: invalid address (fault address: 0x4b20)
    frame #0: 0x0000000000487a38 Main2`stg_IND_STATIC_info + 8
Main2`stg_IND_STATIC_info:
->  0x487a38 <+8>: jmpq   *(%rbx)
    0x487a3a:      nopw   (%rax,%rax)
    0x487a40:      addl   %eax, (%rax)
    0x487a42:      addb   %al, (%rax)
(lldb) register read
General Purpose Registers:
       rax = 0x0000000000000001
       rbx = 0x0000000000004b20
       rcx = 0x0000000000000012
       rdx = 0x00000042001ff070
       rdi = 0x0000004200106179
       rsi = 0x00000000004b2081  MyInteger_zdfToMyIntegerInteger_closure + 1
       rbp = 0x00000042001052b8
       rsp = 0x00007fffffff79a8
        r8 = 0x0000004200104198
        r9 = 0x0000000000000000
       r10 = 0x0000004200104e00
       r11 = 0x0000004200104e40
       r12 = 0x00000042001061a0
       r13 = 0x00000000004bd218  Main2`MainCapability + 24
       r14 = 0x0000004200106179
       r15 = 0x00000042001050c0
       rip = 0x0000000000487a38  Main2`stg_IND_STATIC_info + 8
    rflags = 0x0000000000010202
        cs = 0x0000000000000033
        fs = 0x0000000000000000
        gs = 0x0000000000000000
        ss = 0x000000000000002b
        ds = 0x0000000000000000
        es = 0x0000000000000000

Steps to reproduce

https://github.com/serokell/weird-ghc

• git clone https://github.com/serokell/weird-ghc && cd weird-ghc
• ./bug.sh 1 or ./bug.sh 2

Environment

• GHC version used: 8.2.2, 8.4.4, 8.6.4, c9756dbf1e (2018-12-18), b1662e812c (2019-01-29)