Upgrade 10.5->10.6 : db crash BUS ERROR (sig 10), reproducible

Hi,
after upgrading from 10.5 to 10.6.2, database now says this:

Mar 7 13:55:25 <local0.info> edge postgres[1820]: [7-1] :[] LOG: database system was shut down at 2019-03-07 13:43:29 CET
Mar 7 13:55:25 <local0.info> edge postgres[1816]: [7-1] :[] LOG: database system is ready to accept connections
Mar 7 13:58:43 <local0.info> edge postgres[1816]: [8-1] :[] LOG: worker process: parallel worker for PID 3526 (PID 3527) was terminated by signal 10: Bus error
Mar 7 13:58:43 <local0.info> edge postgres[1816]: [9-1] :[] LOG: terminating any other active server processes
Mar 7 13:58:43 <local0.info> edge postgres[1816]: [10-1] :[] LOG: archiver process (PID 1824) exited with exit code 1
Mar 7 13:58:43 <local0.info> edge postgres[1816]: [11-1] :[] LOG: all server processes terminated; reinitializing
Mar 7 13:58:45 <local0.info> edge postgres[3531]: [12-1] :[] LOG: database system was interrupted; last known up at 2019-03-07 13:55:25 CET
Mar 7 13:58:51 <local0.info> edge postgres[3534]: [12-1] [unknown]:[unknown][192.168.98.3(45111)] LOG: connection received: host=192.168.98.3 port=45111
Mar 7 13:58:51 <local0.err> edge postgres[3534]: [13-1] rapppmcf:fin[192.168.98.3(45111)] FATAL: the database system is in recovery mode
Mar 7 13:58:51 <local0.info> edge postgres[3535]: [12-1] [unknown]:[unknown][192.168.98.3(45112)] LOG: connection received: host=192.168.98.3 port=45112
Mar 7 13:58:51 <local0.err> edge postgres[3535]: [13-1] rapppmcf:fin[192.168.98.3(45112)] FATAL: the database system is in recovery mode
Mar 7 13:58:57 <local0.info> edge postgres[3531]: [13-1] :[] LOG: database system was not properly shut down; automatic recovery in progress
Mar 7 13:58:58 <local0.info> edge postgres[3531]: [14-1] :[] LOG: redo starts at 2C/C600008C
Mar 7 13:59:10 <local0.info> edge postgres[1816]: [12-1] :[] LOG: startup process (PID 3531) was terminated by signal 10: Bus error
Mar 7 13:59:10 <local0.info> edge postgres[1816]: [13-1] :[] LOG: aborting startup due to startup process failure
Mar 7 13:59:11 <local0.info> edge postgres[1816]: [14-1] :[] LOG: database system is shut down

This is repeatable. DB starts normally, I start first application fine,
start second application fine, start third application: KABOOM!

Reinstalled 10.5 for now, so it runs again.

Time to read the relnotes:
> When building on i386 with the clang compiler, require -msse2 to be
> used (Andres Freund)
> This avoids problems with missed floating point overflow checks.

What the hell does that mean? Does it concern the build process? Or
the operation? Why does it only concern the Clang? And what is SSE2
concerned with?

Or, is this a strangely cryptic statement, which, after proper decryption,
should actually read:
// "Beginning with the upgrade from 10.5 to 10.6, postgreSQL can no
// longer run on platforms that do not provide SSE2" ???

The point here is, my third application works with lots of floating
point stuff. The other two do not.

Further investigation to followup ASAP.

PMc