I was testing the new git release to test the fps drop with transitions and the crash with fast reverse. I also have freeze (not crash) if I use fast reverse. It doesn't happen every time; it happens more often if transitions are present and if I use "Perpetual session". No problem in X11, only with X11-OpenGL. For me the problem of transitions is solved: there is only a small drop in fps, but it is instantaneous and immediately restored. The drop is more accentuated in Reverse, but immediately restored. Even with "play every frame" I have a more pronounced drop but this is also immediately restored. But I noticed that simply putting a transition in timeline leads to some messages in terminal (Messages that are repeated for each transition applied). This happens only if "Perpetual session" is active: Cinelerra Infinity - built: Sep 13 2020 09:14:25 git://git.cinelerra-gg.org/goodguy/cinelerra.git (c) 2006-2019 Heroine Virtual Ltd. by Adam Williams 2007-2020 mods for Cinelerra-GG by W.P.Morrow aka goodguy Cinelerra is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. There is absolutely no warranty for Cinelerra. MainUndo::update_undo_before 92 "": must be on an after entry to do this. size=39 UndoStack::dump 0 0x561f28222b70 perpetual load 790 ffffffff * 1 0x561f28224090 perpetual load 790 ffffffff 2 0x561f28223450 882 0000 3 0x561f2823d0a0 transition 790 0001 4 0x561f281fdf40 transition 524 0001 5 0x561f281fdee0 transition 524 0001 6 0x561f285277a0 transition 272 0001 7 0x561f2853f6c0 transition 272 0001 8 0x561f28408630 transition 4 0001 k 9 0x561f283135d0 transition 11968 0001 10 0x561f28526680 transition 1510 0001 11 0x561f284d4bb0 perpetual load 330 ffffffff 12 0x561f283e68f0 perpetual load 330 ffffffff 13 0x561f28312710 record patch 330 0004 14 0x561f28431bf0 record patch 185 0004 15 0x561f2854de50 record patch 185 0004 16 0x561f28551da0 record patch 52 0004 17 0x561f28526780 move track down 52 ffffffff 18 0x561f28456bc0 move track down 174 ffffffff 19 0x561f28408500 move track up 174 ffffffff 20 0x561f28385d30 move track up 40 ffffffff 21 0x561f28539df0 move track up 40 ffffffff k 22 0x561f284d0ed0 move track up 11874 ffffffff 23 0x561f28349d80 swap tracks down 1276 ffffffff k 24 0x561f2a914230 swap tracks down 11874 ffffffff 25 0x561f2a911f10 swap tracks up 1564 ffffffff 26 0x561f285299f0 swap tracks up 294 ffffffff 27 0x561f28391c20 move tracks down 294 ffffffff 28 0x561f28398b00 move tracks down 464 ffffffff 29 0x561f282ea000 move tracks up 464 ffffffff 30 0x561f2a90cc50 move tracks up 294 ffffffff 31 0x561f2a90a930 record patch 294 0004 MainUndo::update_undo_after 142 "perpetual load": must be on a before entry to do this. size=40 UndoStack::dump 0 0x561f2846e9a0 790 0000 * 1 0x561f28222b70 perpetual load 790 ffffffff 2 0x561f28224090 perpetual load 790 ffffffff 3 0x561f28223450 882 0000 4 0x561f2823d0a0 transition 790 0001 5 0x561f281fdf40 transition 524 0001 6 0x561f281fdee0 transition 524 0001 7 0x561f285277a0 transition 272 0001 8 0x561f2853f6c0 transition 272 0001 9 0x561f28408630 transition 4 0001 k 10 0x561f283135d0 transition 11968 0001 11 0x561f28526680 transition 1510 0001 12 0x561f284d4bb0 perpetual load 330 ffffffff 13 0x561f283e68f0 perpetual load 330 ffffffff 14 0x561f28312710 record patch 330 0004 15 0x561f28431bf0 record patch 185 0004 16 0x561f2854de50 record patch 185 0004 17 0x561f28551da0 record patch 52 0004 18 0x561f28526780 move track down 52 ffffffff 19 0x561f28456bc0 move track down 174 ffffffff 20 0x561f28408500 move track up 174 ffffffff 21 0x561f28385d30 move track up 40 ffffffff 22 0x561f28539df0 move track up 40 ffffffff k 23 0x561f284d0ed0 move track up 11874 ffffffff 24 0x561f28349d80 swap tracks down 1276 ffffffff k 25 0x561f2a914230 swap tracks down 11874 ffffffff 26 0x561f2a911f10 swap tracks up 1564 ffffffff 27 0x561f285299f0 swap tracks up 294 ffffffff 28 0x561f28391c20 move tracks down 294 ffffffff 29 0x561f28398b00 move tracks down 464 ffffffff 30 0x561f282ea000 move tracks up 464 ffffffff 31 0x561f2a90cc50 move tracks up 294 ffffffff Note: I didn't use move/swap tracks up or down! I don't understand why these entries are present.