failed to open stream: No such file or directory in advagg_missing_send_saved_file() (line 116 of advagg/advagg.missing.inc

I get this warning on various pages.

Warning: file_get_contents(/sites/mysite/files/advagg_css/css__QiciioHPNmLYXSStJy6o3WGJYt65TVEzuHsLuIFWSLQ__gniHNr9FQSQ2qCagYr6zjoAYeDvBS5-V2Ya10ABpHY0__CDngsR7-TZkSNEzJXP_ICu75XBxyQPhLt_V1wem1GLY.css): failed to open stream: No such file or directory in advagg_missing_send_saved_file() (line 116 of advagg/advagg.missing.inc).

But the file exists
-rw-rw-r-- 1 www-data www-data 134023 Aug 28 18:38 sites/mysite/files/advagg_css/css__QiciioHPNmLYXSStJy6o3WGJYt65TVEzuHsLuIFWSLQ__gniHNr9FQSQ2qCagYr6zjoAYeDvBS5-V2Ya10ABpHY0__CDngsR7-TZkSNEzJXP_ICu75XBxyQPhLt_V1wem1GLY.css