In mysql 5.7 it's required to have the order by fields to be present in the select statement when using DISTINCT. This is because the ONLY_FULL_GROUP_BY setting is turned on by default. I couldn't find where to fix this but it seems to be related to the sfPager or sfDoctrinePager, and I'm sure there are other places in the code this could happen.
SQLSTATE[HY000]: General error: 3065 Expression #1 of ORDER BY clause is not in SELECT list, references column 'time_dev.u3.bio' which is not in SELECT list; this is incompatible with DISTINCT. Failing Query: "SELECT DISTINCT u3.id, SUM(u4.value) AS u4__0 FROM user u3 INNER JOIN user_skill u4 ON u3.id = u4.user_id WHERE u3.first_name IS NOT NULL AND u3.cache_thumbs >= 0 AND u3.id IN (1, 14, 22, 35, 58, 79, 87, 91, 97, 101, 125, 178, 190, 235, 261, 267, 277, 280, 287, 341, 410, 438, 483, 488, 489, 492, 496, 510, 526, 562, 573, 579, 1085, 1134, 1147, 1193, 1195, 1285, 1542, 1558, 1643, 1664, 1842, 1843, 2206, 2268, 2387, 2442, 2475, 2491, 2566, 2678, 2714, 3059, 3202, 3258, 3677, 3723, 4176, 4177, 4183, 4187, 4189, 4230, 4244, 4271, 4288, 4322, 4335, 4361, 4362, 4372, 4374, 4388, 4402, 4407, 4419, 4443, 4444, 4450, 4465, 4475, 4484, 4488, 4489, 4510, 4517, 4531, 4538, 4548, 4566, 4573, 4617, 4618, 4621, 4622, 4624, 4631, 4638, 4653, 4664, 4669, 4672, 4673, 4680, 4681, 4690, 4695, 4723, 4738, 4739, 4745, 4772, 4779, 4789, 4796, 4812, 4821, 4822, 4823, 4827, 4847, 4860, 4871, 4877, 4880, 4887, 4913, 4921, 4923, 4944, 4983, 4984, 4987, 5002, 5004, 5007, 5011, 5019, 5021, 5023, 5028, 5029, 5036, 5043, 5056, 5065, 5083, 5095, 5096, 5116, 5137, 5155, 5195, 5204, 5214, 5221, 5231, 5239, 5274, 5275, 5287, 5293, 5299, 5306, 5344, 5345, 5346, 5348, 5354, 5355, 5358, 5359, 5371, 5374, 5394, 5395, 5403, 5408, 5429, 5430, 5434, 5447, 5464, 5474, 5481, 5497, 5514, 5520, 5550, 5551, 5556, 5557, 5558, 5567, 5569, 5610, 5622, 5629, 5633, 5636, 5640, 5641, 5646, 5650, 5674, 5677, 5684, 5696, 5697, 5702, 5714, 5728, 5731, 5735, 5747, 5750, 5761) AND u4.value >= 1 AND u4.skill_id IN (1, 2, 3, 4, 5, 6, 7, 31, 39, 51, 52, 54) GROUP BY u3.username ORDER BY CASE WHEN u3.bio IS NULL OR u3.bio='' THEN 1 ELSE 0 END, u4__0 DESC LIMIT 20"