I notice that the file fr-CA-DefaultOrderConfirmationPlainTextEmailTemplate.config is encoded as utf8 without BOM
Possibly in the context of smtp messages it is not detecting the encoding correctly, changing it to utf-8 with BOM using a text editor like Notepad++ might solve it, I would try that since you say other messages such as contact form are being sent correctly. With BOM just adds some bytes to the beginning of the file that make it easier to sniff/detect the encoding, without that it may be seeing the file as ansi and losing some of the chars.
If you find that works let me know and I will change the encoding format of that file here.
Hope that helps,