This is a very sensible question I wish more people would ask.
In some situations an error 70 can be a problem reading stored images on a memory card.
In other situations, it can indicate a more serious problem. I would not rely on a firmware update to resolve an error 70 condition. You'd be better off resetting the camera to defaults. I would also try a different battery and new or freshly formatted memory card. An error 70 is usually a software issue, but the underlying cause can be hardware related. If the above suggestions don't help, the camera should be inspected by Canon.
Depending on the serial number, some 70Ds were prone to this error.
Canon stopped repairing the PCB for free in December of 2022.
Bay Area - CA
~R5 C (184.108.40.206) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel 8 ~CarePaks Are Worth It
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.