To check if the app's data is causing this odd behavior, I suggest resetting it. This process plays the same role as clearing the cache from your web browser. They collect cache (cookies) to save you time when loading repetitive data and images.
The steps to do this may differ depending on the OS you're using.
For Andriod, here's how:
From the More Options ⋮, select Settings.
Tick Refresh Data, then choose Yes.
From the Menu ☰, select Help & Feedback.
Click Refresh Data, and then select Refresh.
You can also do it in your device settings. Here's how:
Go to your device's Settings, select Apps (varies by device).
Choose QuickBooks app from the list, and then pick Storage.
Finally, hit clear data.
Go to your device's Settings, select Setting General iPhone Storage.
Choose an app that's taking up a lot of space.
To free up the storage without deleting the documents and data for the app, select the Offload App.
Once done, try to open the invoice(s) again to double-check.