I found a sequence this morning that is 100% reproducible.
1. I have 3 project windows open with multiple files in each (I'm not sure this matters but I'll record it anyways).
2. All project windows are minimized except the first one that you see under the Window list in the menu.
3. Start with the visible window at smaller than screen size and aligned to the left of the screen
a) Add some text and Cmd-S
b) Drag the right border to widen the window a bit
c) Repeat a-b
d) Click Zoom button to expand the window to fill the screen
e) Add some text and Cmd-S
f) Quit TM
g) Start TM
h) Click on Zoom and shrinkamadoodle (see attachment on how it looks)
Any exceptions in console?
No exceptions. I do get these that's not related to this issue though.
2014-10-14 10:50:23.207 PM TextMate[759]: CGContextScaleCTM: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
2014-10-15 10:16:17.049 AM WindowServer[302]: disable_update_timeout: UI updates were forcibly disabled by application "TextMate" for over 1.00 seconds. Server has re-enabled them.
2014-10-15 10:16:23.704 AM WindowServer[302]: common_reenable_update: UI updates were finally reenabled by application "TextMate" after 7.66 seconds (server forcibly re-enabled them after 1.00 seconds)
2014-10-15 10:16:49.004 AM TextMate[400]: Couldn't contact spell checker for Canadian English
Do you click the zoom button after opening a project (which opens in the non-zoomed size)?
The longer sequence listed above provides more detail.