I tried to test the QGIS Offline Editing Plugin but it appears not to work at all.
I'm using qgis 2.14.3 running on a Lenovo Yoga 900 and Windows 10 on the client side. For the server I'm running Ubuntu 16.04 Postgresql 9.5 and PostGIS 2.2 on the same machine using Virtualbox 5.
The workflow: import a shapefile into PostGIS using QGIS desktop>DBManager. After loading the layer I Click the 'toggle editing' button and select a feature so that it is highlighted yellow. I then click the 'node tool' button, select a node and move it to a random spot. At this point, I do not save the change as I just want to ensure editing works for PostGIS. Editing seems to behave as expected for PostGIS layer.
I then select the layer in the 'Layers Panel', click the 'Database' menu item and select 'Offline editing>Convert to offline project'. A .sqlite file is created on my local drive and the Layer has '(offline)' appended to its title in the 'Layers Panel'.
Editing (Offline): I attempted to follow the workflow above however, when I select a feature another random feature is selected (highlighted yellow)! If I pan then others features are highlighted yellow as if panning changes the feature selected!! If I click the 'Node Tool' and try to select a node on the highlighted feature then no nodes are selected (stay as crosses and not cross and box) and the edit tools seems to stop working totally unless I reload the project file.
I have tried this on three separate layers including 2 polygon and one line. The behaviour is the same for all three layers.
I checked 'Log Messages Panel' under the 'Processing' tab I have this warning "OTB was not found or is not correctly installed." I'm not sure if the Offline Plugin uses Orfeo Toolbox??
I also found this post that seems very similar but there doesn't seem to a resolution: Alternatives to Offline Editing Plugin of QGIS?