Cannot read property 'reject' of null

Hi,

since yesterday, we have been having an error where some of our embedded reports aren't loading the data.

The spinner that indicates data loading for individual visuals keep spinning and the error "Cannot read property 'reject' of null" is thrown on reportEmbed.min.js

Uncaught TypeError: Cannot read property 'reject' of null
at XMLHttpRequest.xhr.onreadystatechange [as __zone_symbol__ON_PROPERTYreadystatechange] (reportEmbed:452)
at XMLHttpRequest.g (reportEmbed.min.js:1)
at t.invokeTask (reportEmbed.min.js:1)
at e.runTask (reportEmbed.min.js:1)
at e.invokeTask [as invoke] (reportEmbed.min.js:1)
at f (reportEmbed.min.js:1)
at XMLHttpRequest.h (reportEmbed.min.js:1)
xhr.onreadystatechange @ reportEmbed:452
g @ reportEmbed.min.js:1
t.invokeTask @ reportEmbed.min.js:1
e.runTask @ reportEmbed.min.js:1
e.invokeTask @ reportEmbed.min.js:1
f @ reportEmbed.min.js:1
h @ reportEmbed.min.js:1
XMLHttpRequest.send (async)
g @ reportEmbed.min.js:1
t.scheduleTask @ reportEmbed.min.js:1
e.scheduleTask @ reportEmbed.min.js:1
e.scheduleMacroTask @ reportEmbed.min.js:1
(anonymous) @ reportEmbed.min.js:1
o.(anonymous function) @ reportEmbed.min.js:1
getConceptualSchema @ reportEmbed:458
xhr.onreadystatechange @ reportEmbed:373
XMLHttpRequest.send (async)
getModelsAndExploration @ reportEmbed:392
startFrontLoadReportEmbed @ reportEmbed:96
receiveMessage @ reportEmbed:143

I can also see in the sources that everytime I reload a report it creates a new "reportEmbed" section under "sources" in the debugger.

It seems to be able to load fine the first time if you do a "clear cache and hard reload" but from then on it throws the error.

Does anyone have this problem?

The problem is happening on a report doing an import query on the sql server and a report doing a live connection to an ssas server through an on-premise data gateway.