IRM issue from 8.1.1.4 to 15.0

hello,

we met one issue executing IRM when updating  siebel from 8.1.1.4 to 15.0.

upgwiz log is the following:

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Status Message ( )

Trace    TracingInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    CFG Entry (Status=Complete)

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Action completed (Take backup of DB and update DB stats)

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Status Message ( )

Trace    TracingInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    CFG Entry (Status=Complete)

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Action completed (Execute Incremental Repository Merge)

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Status Message ( )

Trace    TracingInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    CFG Entry (Status=Error)

UpgradeLog    UpgradeInfo    3    00000002568b0c04:0    2016-01-05 19:47:00    Action begin ()