Can't stretch mask in DS2018 SP0 & SP1

Hello, since Draftsight 2018 SP0 (same problem with SP1), I cannot stretch entities like masks.
In previous versions (DS2017), stretching a group or selection of entities containing a mask was not a problem. The mask was stretched with other entities.
But now with DS 2018, it doesn't work anymore, I get an error when I want to specify the starting point of the stretching.

I've noted that if I delete the mask and I create a new one, it works fine.
But the problem is that I have to work on several drawings made in previous versions and it's a huge job to replace "old" mask by new ones...
Any idea?

I was hoping that SP1 would have solved the bug but unfortunately not ...

Best regards

Alain