When attempting to checkout a copy of a complete read only model user receives message in Error dialog box:
"Memory corruption in model, cannot complete request."
Hitting the OK button just closes the model and there is no option to save the model and continue.

This has occurred shortly after migrating some Common Action Blocks from an upstream model.
From this KB article installing Gen 8.5 PTF TSN85028/RO91356 should enable a save option but it has no effect: Gen toolset checkout error "The model ... may have been corrupted"
Also see same result when try to open model with Gen 8.6 Toolset with PTF IRN86100/RS94237 installed.

As a workaround, the user can successfully checkout a subset with the PSteps in Full/System Test/Read, which pulls down about 70% of the model. However, there are times when they need to pull down the entire model to do some wide ranging changes.

Gen Toolset
8.5, 8.6

This message does not represent an actual model corruption, rather a memory error reported by the Toolset memory validation. 

The fix for problem CGTS/1498 made in 8.5 PTF TSN85028/RO91356 and 8.6 PTF TSN86002/RO92004 which enabled flow to the "save" logic rather than just closing the model was only for one particular scenario of memory validation failure. Other such scenarios may still exist and only by researching the model checkout.trn files that cause such problems can Engineering develop further fixes.

For this type of problem if it persists after installing the latest Toolset PTFs then it is suggested to re-subset differently so the memory structures fall differently (not just a matter of subset size). Once more work is done on the model & a new checkout.trn is created it maybe that the problem will not reoccur.
If the problem continues then to receive further assistance from CA Gen Technical Support with suggested workarounds or a resolution please create a new Support case.

Update March 28 2019:
An additional fix for another "Memory corruption in model" scenario is now available in Gen 8.5 PTF TSN85044/SO07844.

Gen 8.6 Toolset Messages: The model variable may have been corrupted. Do you still want to save it?