Lines Chart Dots Disappear When Published

Hello All,

Firstly, apologies if I get the terminology wrong, I'm a fairly new Power BI user having crossed over from Qlik.

We've just started to get this strange issue when publishing a report. We're using a line chart that was developed for us to give a special type of statistical analysis. It uses a number of different fields in the y-axis to give different lines, three of these fields are value, value_orange and value blue, the colours signifying a statistical rule break. The value always has a number in the field, the value_orange and value_blue only have a number if there is a rule break and are otherwise empty. This first image shows the graph working perfectly in the Power BI Desktop app...

Desktop chart:

However, when we publish the report in a workspace, the dots all disappear, as per the below image. This has been previously working without any issues for about a year but suddenly stopped last week a some point. If you hover over the points then the dots do still appear. 

Published chart: 

Important to mention, that the dots are created in ( visualizations > format visual > visual > lines ) using a round join type and with the value field also having a line to creat the grey lines between the dots, couple of small screenshots below.

We can get around this by turning on markers but we've got thousands of charts like this across hundreds of reprots and it would take a very long time to fix everything. In the meantime it's making our products useless to the end users.

Does anyone have any ideas why this might be happening? or experienced similar? We don't want to start changing everything by turning on markers if this is just a temporary bug. Any help would be greatly appreciated.