[roger64]

Thanks for your reply.

I use the binaries provided by the Calibre Linux script, currently at 7.1.

In the joint png screenshot you can see the error message I am getting when I ask Calibre to make a subset.

In the zip, I provided two examples of the same ePub3. This book was published by me on MR in 2018 and I slightly modify it for this purpose. As there are nineteenth century letters, the use of an old numerotation makes sense.

- The first one is before subsetting, where you can see, for example, that the Date at the beginning of each chapter uses the old numerotation (open-type).
- The second one named (calibre-subset) is after subsetting where you can see that the Date at the beginning of each chapter does not use anymore the old numerotation.

So this error message seems to have an impact, even if indirect, on the open-type display.