The Bug
The new mineshaft generations use oak wood (the bark one) instead of oak logs as the support pillars. This was fixed in the Java experimental snapshots.
MCPE-125133
Mineshaft support pillars are made out of bark oak wood, not logs
Resolved
Fixed
16
(Unassigned)
509996
Confirmed
Multiple
experimental, vanilla-parity
1.18.0.22 Beta, 1.18.0.21 Beta, 1.18.0.20 Beta, 1.17.40.20 Beta, 1.17.30.24 Beta, ..., 1.17.10, 1.17.10.21 Beta, 1.17.0.54 Beta, 1.16.230.56 Beta, 1.17.40
1.18.0.24 Beta, 1.18.0
Retrieved
Simply, new cave generation in Bedrock has all the bugs that Java had when they were first added.