[Pound Mailing List] Odd load balancing

While continuing to investigate my gradual slowdown issue (still no answers
I'm confident off), I've noticed that Pound doesn't seem to be distributing
requests fairly between backends. As an example:

     24. Session VAXTUawYMhQAACit1ncAAAAO -> 0
     25. Session VAXODawYMhQAACLlWeoAAAAR -> 0
     26. Session VAXL36wYMhUAABc04XMAAABD -> 1
     27. Session VAXMbqwYMhQAAB@ZCGkAAAAF -> 1
     28. Session VAXNc6wYMhUAABphPnQAAACH -> 1
     29. Session VAXM4qwYMhUAABi219QAAAAN -> 1
     30. Session VAXJGKwYMhUAAA-StA8AAABE -> 1
     31. Session VAXMpawYMhUAABgtHwcAAAAS -> 1
     32. Session VAXIaqwYMhUAAA5FXq0AAACZ -> 1
     33. Session VAXLa6wYMhUAABSRXfQAAAAU -> 1
     34. Session VAXHwKwYMhUAAA4QDkAAAABk -> 1
     35. Session VAXMLawYMhUAABfzdG8AAAAP -> 1
     36. Session VAXKpKwYMhUAABQ6GcsAAAAM -> 1
     37. Session VAXHj6wYMhUAAA4bLxgAAABv -> 1
     38. Session VAXIPqwYMhUAAA3OQPMAAAAg -> 1
     39. Session VAXGGawYMhUAAAsD3hAAAADo -> 1
     40. Session VAXMK6wYMhUAABdQA0wAAAAG -> 1
     41. Session VAXLkqwYMhUAABSlh8wAAAAz -> 1
     42. Session VAXLqawYMhUAABcf08IAAAAq -> 1
     43. Session VAXKjawYMhQAABexeFkAAAAT -> 1
     44. Session VAXHEqwYMhUAAA1Vzz0AAAAk -> 1
     45. Session VAXGAawYMhUAAAodbjEAAAAp -> 1
     46. Session VAXIwKwYMhUAAA7sRMMAAAAK -> 1
     47. Session VAXIGawYMhUAAA4WLegAAABq -> 1
     48. Session VAXG06wYMhUAAAldgqkAAABR -> 1
     49. Session VAXKYqwYMhUAABAQTLcAAACA -> 1
     50. Session VAXGQawYMhUAAAkoL6wAAAAU -> 1
     51. Session VAXJpawYMhQAABLrci0AAAAE -> 1
     52. Session VAXG@awYMhUAAAr52FsAAABu -> 1
     53. Session VAXLgqwYMhUAABcm1iMAAAA1 -> 1
     54. Session VAXI2awYMhQAABAx-j8AAAAL -> 1
     55. Session VAXMX6wYMhQAAB72RZ8AAAAE -> 1
     56. Session VAXJHqwYMhUAAA-LorIAAAA9 -> 1
     57. Session VAXMv6wYMhUAABlgehAAAACk -> 1
     58. Session VAXI9awYMhUAAA-Xrq4AAABJ -> 1
     59. Session VAXNY6wYMhQAACLlVW4AAAAR -> 0
     60. Session VAXLGqwYMhQAABoJrBIAAAAM -> 1
     61. Session VAXGiawYMhUAAAkxLhgAAAAg -> 1
     62. Session VAXMO6wYMhUAABg7IeIAAAAk -> 1
     63. Session VAXHQawYMhUAAA1c90sAAAAE -> 1
     64. Session VAXMnqwYMhUAABfwdRMAAAAM -> 1
     65. Session VAXIu6wYMhUAAA47UPwAAACP -> 1


DynScale is left on its default setting (off). I can't see any other
explanations for this unexpected behaviour. Any thoughts?

Jon