diff --git a/polymer/eduke32/build/src/engine.c b/polymer/eduke32/build/src/engine.c
index 561658957..8158c28b8 100644
--- a/polymer/eduke32/build/src/engine.c
+++ b/polymer/eduke32/build/src/engine.c
@@ -12194,17 +12194,27 @@ void updatesectorexclude(int32_t x, int32_t y, int16_t *sectnum, const uint8_t *
     *sectnum = -1;
 }
 
+// new: if *sectnum >= MAXSECTORS, *sectnum-=MAXSECTORS is considered instead
+//      as starting sector and the 'initial' z check is skipped
+//      (not initial anymore because it follows the sector updating due to TROR)
 void updatesectorz(int32_t x, int32_t y, int32_t z, int16_t *sectnum)
 {
     walltype *wal;
     int32_t i, j, cz, fz;
 
-    if ((*sectnum >= 0) && (*sectnum < numsectors))
+    if ((uint32_t)(*sectnum) < 2*MAXSECTORS)
     {
+        int32_t nofirstzcheck = 0;
+
+        if (*sectnum >= MAXSECTORS)
+        {
+            *sectnum -= MAXSECTORS;
+            nofirstzcheck = 1;
+        }
+
         // this block used to be outside the "if" and caused crashes in Polymost Mapster32
         getzsofslope(*sectnum, x, y, &cz, &fz);
-        if ((z >= cz) && (z <= fz))
-            if (inside(x,y,*sectnum) != 0) return;
+
 #ifdef YAX_ENABLE
         if (z < cz)
         {
@@ -12219,6 +12229,8 @@ void updatesectorz(int32_t x, int32_t y, int32_t z, int16_t *sectnum)
                 { *sectnum = i; return; }
         }
 #endif
+        if (nofirstzcheck || ((z >= cz) && (z <= fz)))
+            if (inside(x,y,*sectnum) != 0) return;
 
         wal = &wall[sector[*sectnum].wallptr];
         j = sector[*sectnum].wallnum;
diff --git a/polymer/eduke32/source/player.c b/polymer/eduke32/source/player.c
index 1d17814bf..f1524a4ba 100644
--- a/polymer/eduke32/source/player.c
+++ b/polymer/eduke32/source/player.c
@@ -4529,7 +4529,6 @@ void P_ProcessInput(int32_t snum)
     int32_t fz, cz, hz, lz, truefdist, x, y, psectlotag;
     uint8_t *kb = &p->kickback_pic;
     int16_t tempsect;
-    int32_t jetpackdz = 0;
 
     if (g_player[snum].playerquitflag == 0)
         return;
@@ -4929,7 +4928,6 @@ void P_ProcessInput(int32_t snum)
         if (p->jetpack_on < 11)
         {
             p->jetpack_on++;
-            jetpackdz -= (p->jetpack_on<<7);
             p->pos.z -= (p->jetpack_on<<7); //Goin up
         }
         else if (p->jetpack_on == 11 && !A_CheckSoundPlaying(p->i,DUKE_JETPACK_IDLE))
@@ -4945,7 +4943,6 @@ void P_ProcessInput(int32_t snum)
             VM_OnEvent(EVENT_SOARUP,p->i,snum, -1);
             if (aGameVars[g_iReturnVarID].val.lValue == 0)
             {
-                jetpackdz -= j;
                 p->pos.z -= j;
                 p->crack_time = 777;
             }
@@ -4958,7 +4955,6 @@ void P_ProcessInput(int32_t snum)
             VM_OnEvent(EVENT_SOARDOWN,p->i,snum, -1);
             if (aGameVars[g_iReturnVarID].val.lValue == 0)
             {
-                jetpackdz += j;
                 p->pos.z += j;
                 p->crack_time = 777;
             }
@@ -5373,33 +5369,20 @@ HORIZONLY:
     else
     {
 #ifdef YAX_ENABLE
+        int32_t sect = p->cursectnum;
+        int16_t cb, fb;
+
+        if (sect >= 0)
+            yax_getbunches(sect, &cb, &fb);
+
         // this updatesectorz conflicts with Duke3d's way of teleporting through water,
         // so make it a bit conditional... OTOH, this way we have an ugly z jump when
         // changing from above water to underwater
-        if (p->cursectnum >= 0 && !(sector[p->cursectnum].lotag==1 &&
-                                    p->on_ground && yax_getbunch(p->cursectnum, YAX_FLOOR)>=0))
+        if (sect >= 0 && !(sector[sect].lotag==1 && p->on_ground && fb>=0))
         {
-            int32_t tmpdz = 0;
-
-            // Do updatesectorz only if ceiling/floor bunchnum is >= 0. Otherwise, unwanted
-            // side-effects like dying when jumping into a lotag==1 sector or on other
-            // occasions can occur.
-            // The 'if' is divided in two disjunct cases (jetpack off or on), because we can't
-            // trust p->vel.z when we're flying. In this case, jetpackdz gives the z delta for
-            // this tic.
-            // The (!shrunk || ...) part is so that we don't 'squish' when taking off shrunk.
-            if (p->jetpack_on)
-            {
-                if (!shrunk || p->jetpack_on==11)
-                    tmpdz = jetpackdz;
-            }
-            else if (!p->jetpack_on && p->vel.z)
-            {
-                tmpdz = p->vel.z;
-            }
-
-            if (tmpdz && yax_getbunch(p->cursectnum, (tmpdz>0))>=0)
+            if ((fb>=0 && !(sector[sect].floorstat&512)) || (cb>=0 && !(sector[sect].ceilingstat&512)))
             {
+                p->cursectnum += MAXSECTORS;  // skip initial z check, restored by updatesectorz
                 updatesectorz(p->pos.x,p->pos.y,p->pos.z,&p->cursectnum);
             }
         }