Perusing this thread and the bug report linked above I note that the bug tracking shows this has now finally been "fixed".
Comment 29 by project member c.mag...@bug.st, Dec 17 (2 days ago)
Done. Thank you.
Fixed malloc() bug. (Paul Stoffregen) · arduino/Arduino@d457332 · GitHub
Please check the fix.
How will I know when this bug fix has made it into the official downloadable version 1.x.x?
Thanks,
John
(I hate C but love C++. Mainly e.g. because of char* vs String)