We use Philips here, without any issues. One of the problems with getting the DW information out of the headers is that different vendors store it in different places in different versions of their product… So MRtrix3 will check all the places it knows about, and extract the information if found. In your case, I wouldn’t be surprised if the data you have been supplied with has previously been ‘anonymised’ or otherwise converted via a third-party encoder. Anonymising DICOM data is actually a very difficult thing to do without messing up crucial information, most implementations that I’ve come across simply discard any non-standard tags, since they can’t guarantee that these tags don’t contain sensitive information. Unfortunately, that’s where most vendors store information like the DW encoding…
Happy to take a quick look at your data if you want to share them with me? You can send me a private message via this platform with a link to the data, or email to jdtournier@gmail.com.