I've been having this issue for a while now, very inconsistently. When I type strands of text, sometimes the letters appears in the wrong order (I remember it mostly happening when I type text in Safari). One example:
I typed "Install Canon Printer".
I am using an iMac (21.5-inch, Mid 2011) running 10.10.5, with this keyboard:
They keyboard is plugged directly into the iMac (no hub).
Note: Sometimes I type things wrong, but AFAIK I'm not dyslexic.