AFAIK, after 1.4.1 is released, the IBus developers move to the work
of IBus 1.5 (1.4.99).
However, some bugs of 1.4.1 are found and some fixings are committed
into git. At some point, 1.4.2 is released, including all the commits.
https://github.com/ibus/ibus/commits/1.4.y
If you can make sure that 1.4.2 contains regression (rather than
configuration of your system is broken).
Can you spot a commit to blame?
Actually I feel that these commits are rather trivial. They should not
cause serious regression.