[3.6.0] Corrupted output when using Extruder Start G-code / dual extruder

[BigE2]

Application Version
3.6.0

Platform
Windows 7

Printer
Vertex K8400 Dual (used as base for FFCP)

Steps to Reproduce
Add the following code as "Extruder Start G-code" to one of the Extruders. I used Extruder 1. Add a file, prepare and slice as normal. For this, I'm using Extruder 1 as the main extruder, and Extruder 2 for support interface material

Example Code
;Extruder 1 Start G-Code***
M104 S180 T1; Cool T1 to intermediate temperature

Actual Results
3�xtruder 1 Start G-Code
M104 S180 T1; Cool T1 to intermediate temperature

Note the first 2 characters turned to garbage. Sometimes it's the first 3 characters, and sometimes an entire line is missing.

Expected results
The code should read
;Extruder 1 Start G-Code
M104 S180 T1; Cool T1 to intermediate temperature

Additional Information
File to produce issue: Whalebone.zip