I was troubleshooting why some of my custom object record pages were loading in Lightning and others were not when I stumbled upon a unique discrepancy between the XML code for the condition Id = (param) id among my Skuid pages.
For the Non-Working pages, the XML outputted
<conditions> <condition type="param" value="Id" field="Id" operator="=" state="" novaluebehavior="" enclosevalueinquotes="true"/>
</conditions>
For the Working pages, the XML outputted
<conditions> <condition type="param" value="id" field="Id" operator="=" enclosevalueinquotes="true" novaluebehavior=""/>
</conditions>
I'm unclear as to why the page compiler outputted two different XML codes; however, replacing the non-working code with the working code...well works. I did this across all the custom objects where record detail pages weren't loading and they all resolved themselves.