I have a teeth grinder verified to occur in 12.0 and 12.1 64 bit. Using 11gR2 64 bit Oracle client on 64 bit Windows 7.
The problem makes repetitive copy and pasting of numeric values onerous.
First open notepad and type “1.1” and copy the text.
Then open any table in the schema browser and set your cursor into a number field. Paste it once and then (yes too much coffee) accidentally paste it a second time forcing “1.11.1” into the field.
TOAD then goes into a death spiral of OCI error popups from which there is no escape short of forcing TOAD closed with the task manager.
I also checked that this occurs when you just type “1.11.1” into a numeric field.