[GIS] How to install the QField Sync plugin

Question

I am having trouble installing the QField Sync plugin to work with the great QField android app. and would like assistance doing so. The steps I have followed thus far are reproduced below.
(Using QGIS 2.18 via OSGEO4w installer on Windows 7)

When I attempt to install it through the Plugin Manager I get an error message telling me to install the "QGIS2compat" plugin:

http://i.imgur.com/ZilPcBg.png

I select "uninstall" plugin from this dialog.

Then I install the "QGIS2compat" plugin which seems to work properly:

However if I then attempt to install the "QField Sync" plugin afterwards (without restarting) I get the following message:

http://i.imgur.com/Ifi2rMM.png

So I uninstall and, after restarting QGIS (having installed "QGIS2compat" and not "QField Sync") and before QGIS loads fully I get the following error message and "Processing Toolbox" is disabled:

http://i.imgur.com/sajANgT.png

When I try to install the "QField Sync" plugin now, I get the same "UIC" error message as above but I leave it installed anyway and the Plugin Manager tells me that it is "broken" – I also can't find it in any of the Plugin panels/toolbars.

http://i.imgur.com/b1HQkfP.png

So I restart QGIS and get the following error messages in the Log from start up:

http://i.imgur.com/dUtBdAN.png

So I uninstall "QGIS2compat", restart QGIS, the "Processing toolbox" returns but I still have no "QFIELD Sync".

Can anyone help me to install "QField Sync" properly?

[EDIT: Further to the above, now using QGIS version 2.18.11 win7, following similar steps to above, I get the following error:

http://i.imgur.com/d20SKfQ.png]

Answer 1

[EDIT: Unfortunately the answer/fix discussed below is no longer working and the same or similar circumstances to those described in the question above persist ... will re-edit if things change again]

This question/problem has now been answered/fixed!

Either one or both of updating to the latest version of QGIS (2.18.1 in this instance) as well as what seems to be an update to the version of the plugin I was having trouble with has resolved the issue.

At the time of the problem the QField Sync plugin was version 0.4 though the 'Available version ... (in QGIS Official Plugin Repository)' is now: 0.8.7

Thanks to all the wonderful folks at QField (opengis.ch) and on GIS SE!