# Failed Prints - Hazy, blotchy marks on optical window

**URL:** <https://forum.formlabs.com/t/failed-prints-hazy-blotchy-marks-on-optical-window/17253>\
**Category:** Form 2\
**Created:** [February 6, 2018, 1:16pm UTC](https://forum.formlabs.com/t/failed-prints-hazy-blotchy-marks-on-optical-window/17253 "2018-02-06T13:16:37Z")\
**Posts on this page:** 1\
**Showing post:** 21

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**Author:** ![Beth](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.formlabs.com/beth/32/13397_2.png) [@Beth](https://forum.formlabs.com/u/Beth)\
**Post date:** [February 8, 2018, 1:25pm UTC](https://forum.formlabs.com/t/failed-prints-hazy-blotchy-marks-on-optical-window/17253/21 "2018-02-08T13:25:32Z")

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Well at least that’s some progress on the troubleshooting. I think to revert back to a previous firmware you have to manually select the older version when you select update firmware. There’s a thread a bout it here : [How to ROLL BACK FIRMWARE?](http://forum.formlabs.com/t/how-to-roll-back-firmware/16823)

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