Gaps between lines in one axis on small frame members

Trying to print a small frame structure.
on members in one direction there are large gaps between where lines. so where there should be two 0.4mm lines right next to each other to make a 0.8mm wide member the printer instead prints these lines with a gap of about 2mm between them.

these issues don’s show up when i preview the file in cura.

Please help.

Many thanks
Paul4c83ddf4-5d4d-4cc6-a9ee-43f565dd5290 a566cf92-e9af-40a2-a079-bcbae8f13a2e