Rounding errors when scaling when none should occur

Please see video linked below. The selected nodes are precisely placed and I use the shift arrow keys to increase the values of the X in units of 10. The lock icon is enabled to keep the proportions scaled, in this case 1:1 but scaling the item up and down in units of 10 results in the proportions changing.

The video is here. I am using Glyphs Version 2.6.5 (1342)

Does this happen directly after you opened the file?

No. I relaunched Glyphs and tried again. The behaviour is correct if I do this.