I encountered the same problem, and here is my solution. First take the back cover off, it is held by 3 screws: 2 in battery compartment and one under blue Sekonic logo (pry it off). You'll see power/analog board. In my meter a 220 uF capacitor at the battery input has leaked and polluted the board. Here is what it looked like with capacitor removed:
I removed the following elements and cleaned the board thoroughly. I cleaned with isopropyl alcohol, ethyl alcohol or acetone will be fine too. Picture shows cleaned and reassembled board. IC1 and T1 were placed back after cleaning. Other elements were replaced with new ones.
Element values: R1 - 91K, R2 - 510K, R3 - 100K, C2 - 47 nF X7R, all 0805 size.
On the other side the board also needed some cleaning. I removed C1 and VT1 and cleaned with alcohol. VT1 was placed back. C1 was replaced with new one, 10 nF NP0 or X7R type, 0805 size. Defective 220 uF 4V capacitor was replaced with 220 uF 6.3V tantalum capacitor, C size.
Assemble the meter back. After that device works perfectly.