Error is thrown when upgrading from version '2015062101' to '2017101011':
 
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Debug info: Unknown column 'type' in 'mdl_bigbluebuttonbn'

ALTER TABLE mdl_bigbluebuttonbn MODIFY COLUMN welcome LONGTEXT COLLATE utf8mb4_unicode_ci NOT NULL after type

Error code: ddlexecuteerror

 
Thrown on execution of xmldb_bigbluebutton_add_change_field on line 46-7 of db/upgrade.php
 
Issue appears to be that this call comes before the call to the same function on lines 75-6, which adds the "type" field.