The current delay of 30uS is too short to recover any carrier.

In the lmedm04 driver delays were added to overcome carrier lock
problems. The typical delay was 30mS (2 x 15ms register write
0x2c and read 0x24).

Other drivers that use STV0288 don't appear to have any delay are
likely to have also suffered this problem.
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>