changing dimensions is insanely slow

when going through a nether or end portal, or just joining a server, or even just reloading the texture packs with f3+t, it freezes for like 20-30 seconds.
these are the logs while frozen:

[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Flushing download stream
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Shutting down rendering
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.rg.sn.gy.BasicSectionGeometryData]: Attempting to wait for gpu memory to release
[16:04:33] [Render thread/WARN]: [me.cx.vy.ct.ce.rg.sn.gy.BasicSectionGeometryData]: Failed to wait for gpu memory to be freed, this could indicate an issue with the driver
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Shutting down render pipeline
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Flushing download stream
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Render shutdown completed
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.rg.sn.gy.BasicSectionGeometryData]: Creating and zeroing 3395MB geometry buffer driver states 4390MB of free memory
[16:04:33] [Render thread/INFO]: [me.cx.vy.ct.ce.rg.sn.gy.BasicSectionGeometryData]: if your game crashes/exits here without any other log message, try manually decreasing the geometry capacity
[16:05:03] [Render thread/INFO]: [me.cx.vy.ct.ce.rg.sn.gy.BasicSectionGeometryData]: Successfully allocated and zeroed the geometry buffer in 29874ms
[16:05:03] [Render thread/INFO]: [me.cx.vy.ct.ce.VoxyRenderSystem]: Voxy render system created with 3560169472 geometry capacity, using pipeline 'NormalRenderPipeline' with renderer 'MDICSectionRenderer'
[16:05:03] [Render thread/INFO]: Stopping worker threads
[16:05:03] [Render thread/INFO]: Started 10 worker threads
[16:05:03] [Render thread/INFO]: [ETF]: reloading ETF data.
[16:05:03] [Render thread/INFO]: [ETF]: emissive suffixes loaded: {_e}
[16:05:09] [Async Node Manager/INFO]: [me.cx.vy.ct.ce.rg.hl.AsyncNodeManager$ComputeMemoryCopy]: Resizing scratch data buffer to: 2097152
[16:05:09] [Async Node Manager/INFO]: [me.cx.vy.ct.ce.rg.hl.AsyncNodeManager$ComputeMemoryCopy]: Resizing scratch data buffer to: 4194304
[16:05:10] [Async Node Manager/INFO]: [me.cx.vy.ct.ce.rg.hl.AsyncNodeManager$SyncResults]: Expanding scatter update buffer to 24720
[16:05:10] [Async Node Manager/INFO]: [me.cx.vy.ct.ce.rg.hl.AsyncNodeManager$ComputeMemoryCopy]: Resizing scratch data buffer to: 8388608

Reproduce the freeze during a dimension change, server join, or F3+T reload and start with the BasicSectionGeometryData allocation messages in the logs. Trace the shutdown and recreation flow through VoxyRenderSystem and the buffer-related AsyncNodeManager messages. Done means these transitions no longer incur a 20–30 second render-thread stall.