I have similar issues whenever I download any .APK files from androidfilehost.
The files download perfectly, but the APK is unusable. Downloading the same APK through regular opera and the APK is perfectly usable.
Downloading .zip files from github in opera touch downloads a .bin file for some reason. Same link in regular opera downloads the correct .zip file.
There are some consistent issues with Opera touch that would be nice to see fixed. Until then it's hard to use a main browser unfortunately