Storage graph intermittently incorrect

Please describe what you are doing to trigger the bug:
Open Web UI and select Storage page.

Please describe what you expect to happen (but doesn’t):
Expect Size graph to be correct.

Please describe what actually happens (the wrong behaviour):
Size graph of at least one snapshot is missing/incorrect. Missing/incorrect snapshot graph appears after browser refresh.

Excerpt from check log:

           snap | rev |                          | files | bytes | chunks | bytes |   uniq |    bytes |    new |    bytes |
 Keith-Pictures |   1 | @ 2020-10-09 14:02 -hash | 46224 | 1135G | 216049 | 1013G |     30 |  74,414K | 216049 |    1013G |`
 ...
 Keith-Pictures | all |                          |       |       | 228316 | 1064G | 227392 |    1060G |        |          |

Incorrect Size graph:

After browser refresh: