Last value showing up divided by 2

Re this thread:
https://forums.adafruit.com/viewtopic.php?f=58&t=169004

Can recreate using two CPXs, one running this TX demo:
https://github.com/adafruit/Adafruit_CircuitPython_CircuitPlayground/blob/main/examples/circuitplayground_ir_transmit.py
and one running this RX demo:
https://github.com/adafruit/Adafruit_CircuitPython_CircuitPlayground/blob/main/examples/circuitplayground_ir_receive.py

CircuitPython 5.3.1 with library bundle adafruit-circuitpython-bundle-5.x-mpy-20200901.zip.

This is what shows up on the RX side:
```python
Adafruit CircuitPython 5.3.1 on 2020-07-13; Adafruit CircuitPlayground Express with samd21g18
>>>
soft reboot

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Infrared code received: [66, 84, 78, 32]
Infrared code received: [66, 84, 78, 32]
Infrared code received: [66, 84, 78, 32]
Infrared code received: [66, 84, 78, 32]
```
The sequences being TX'd are `[66, 84, 78, 65]` and `[66, 84, 78, 64]`

Start by running examples/circuitplayground_ir_transmit.py and examples/circuitplayground_ir_receive.py on two CircuitPlayground Express boards, using the versions listed in the issue. Compare the transmitted [66, 84, 78, 65] and [66, 84, 78, 64] sequences with the received output; done means the final value is received unchanged.

Written by the indexing model from the issue text.