XRECODE

Could you, please, share that file with me - xrecode@gmail.com?

SOX resampler was not always used when up-sampling.
Please install the latest beta version - viewtopic.php?f=16&t=40

WavPack will encode 32bit int to 32bit int (it only uses integers when encoding).
ALAC supports up to 24bit integer sample format.

What are source and output sample rate values?

Could you, please, send one such DTS file to xrecode@gmail.com (you could use https://wetransfer.com if it's too big)?

Fixed in the latest beta version.

I'm afraid I cannot do this and I've not seen a dsd2pcm converted, which would do this.

Huh, why would you need a 2.8MHz file? 2.8MHz DSD file is equivalent to a 176kHz wav (or, actually, 88Khz).

Could you, please, send the Diagnostic information (it's under About/Diagnostic) to xrecode@gmail.com?

Please install the latest beta version - viewtopic.php?f=16&t=40
There's a new option under Metadata settings "Default covers folder".